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Charlie Thorne and the Lost City


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About The Book

In this sequel to the New York Times bestselling Charlie Thorne and the Last Equation—which #1 New York Times bestselling author Chris Grabenstein called “a real page-burner”—Charlie searches for Charles Darwin’s hidden treasure in South America.

Charlie Thorne is a genius. Charlie Thorne is a fugitive. Charlie Thorne isn’t even thirteen.

After saving the world, Charlie is ready to take it easy in the Galapagos Islands. That is, until she’s approached by the mysterious Esmeralda Castle, who has a code she knows only Charlie can decipher. In 1835, Charles Darwin diverted his ship’s journey so he could spend ten months in South America on a secret solo expedition. When he returned, he carried a treasure that inspired both awe and terror in his crew. Afterward, it vanished, never to be seen again…

But Darwin left a trail of clues behind for those brave and clever enough to search for it. Enter Charlie Thorne. In a daring adventure that takes her across South America, Charlie must crack Darwin’s 200-year-old clues to track down his mysterious discovery—and stay ahead of the formidable lineup of enemies who are hot on her tail.

When an ancient hidden treasure is at stake, people will do anything to find it first. Charlie may be a genius, but is she smart enough to know who she can trust?


Chapter One ONE
Puerto Villamil

Isla Isabela

The Galápagos Islands, Ecuador

Present day

A hammerhead shark slid through the water beneath Charlie Thorne.

Charlie watched it glide below her feet as her surfboard bobbed in the ocean. It was a big shark, about nine feet long, capable of doing some serious damage. But Charlie’s reaction upon seeing it was excitement, rather than fear. Charlie had seen plenty of hammerheads while surfing in Puerto Villamil. Despite their threatening appearance, statistically, she had little reason for alarm as long as she didn’t do anything stupid around them—and Charlie Thorne was as far from stupid as you could get.

Even though she was only twelve, Charlie had an IQ that rivaled that of anyone who had ever lived. In a situation like this, she couldn’t help but analyze the numbers. She knew that out of the billions of people on earth, fewer than twenty died each year from shark attacks; far more humans were killed annually by falling coconuts. But then, few people actively went surfing in shark-infested waters, where the chances of getting attacked were much greater. Most shark attacks were thought to be mistakes; from underneath, a human on a surfboard had a silhouette similar to that of a sea lion, the preferred food of many sharks. So Charlie was always careful; she didn’t surf while she was bleeding, or wear shiny jewelry that a shark might mistake for the flash of fish scales, or thrash around in the water like a wounded animal. Now, watching the hammerhead, she stayed calm and still.

The shark didn’t seem to care about her at all. It certainly knew she was there, but it continued onward as though the thought of consuming her had never even entered its mind. It was paralleling the coastline of Isla Isabela, heading toward a rocky outcropping where the sea lion rookeries were. Why sharks would pass up an easy meal like a human in favor of harder-to-catch prey like a sea lion was unexplained, but most scientists presumed that sharks simply thought humans didn’t taste very good.

Another hammerhead passed beneath Charlie, and another after that. They were both smaller than the first, but not by much.

This didn’t surprise Charlie: Hammerheads often swam in schools, sometimes numbering up to a hundred. She turned on her board to look behind her. Sure enough, more sharks were coming, their large dorsal fins poking above the surface.

Charlie figured it was time to get out of the water. The odds of an accidental attack were rising by the second.

Fortunately, a good-size wave was coming her way, a bulge in the ocean building as it approached the shore. Charlie watched it—and the numbers came to her.

They simply appeared in her mind, as usual: instant calculations of the speed of the wave, the most likely cresting point, and how fast she would need to paddle to put herself there. Puerto Villamil wasn’t home to many other surfers—or many other people, period—but Charlie had already become legendary among the few who lived there. Even surfers with decades of experience mistimed a wave on occasion, but Charlie never did. Somehow, she was always exactly where she needed to be.

Whenever anyone tried to talk to Charlie about how she read the waves so well, she dodged the question. “Tuve suerte” was all she would say. “I was lucky.”

The others surfers knew that no one could be that lucky, but Charlie wouldn’t say anything else. Charlie had barely spoken to anyone in Puerto Villamil since arriving four weeks earlier. No one knew where she was from or why she had come to such a far-flung place—and they certainly didn’t know her age. Since Charlie looked and behaved much older than her years, everyone assumed she was at least eighteen. The only information she had volunteered was that her name was “Mariposa Espina,” which wasn’t true.

Charlie could pass herself off as a native of almost any place on earth, because ethnically, she was a mix of different races—although she didn’t look like one more than any other. Plus, she spoke over a dozen languages and could understand many more. In a single day, while en route to the Galápagos, she had told different people that she was Thai, Greek, Kenyan, Guatemalan, and aboriginal Australian, and no one had questioned her at all.

Fewer than two thousand people lived in Puerto Villamil, so the arrival of one more was of interest to the locals. There were many rumors as to who Charlie really was and why she had ended up there. Many of them were bizarre and outlandish. Although none were anywhere near as bizarre and outlandish as the truth.

Now Charlie lay flat on the board and paddled with her arms, taking care to do so with smooth, strong strokes that wouldn’t startle the hammerheads below her. She headed directly to the spot where she had calculated the wave would break. Sure enough, the swell rose behind her, exactly as she had predicted, and grew into a ten-foot wall of water. Charlie quickly leapt to her feet upon the board, caught the front slope of the wave, and expertly rode down it. As the wave broke, she surfed right through the curl. She stayed upright all the way to shore, even as the wave collapsed upon itself behind her, then slid into the shallow water and calmly stepped off the board and onto the beach as casually as though she were stepping off a bus onto the curb.

The locals gathered on the shore watched with amazement. Charlie had been a novice surfer when she had arrived in Puerto Villamil. Even though she had been able to spot where the waves would break, she hadn’t been able to ride them. But within a few weeks, using her natural athleticism and her unnatural skill at reading the waves, she was surfing better than most people could after years of practice. The people watching her now shook their heads and uttered the name they all called her behind her back. “Perfecta.”

It was warm on the beach, as usual. Since Isla Isabela sat directly on the equator, the temperature didn’t vary much. Charlie peeled off the neoprene suit she had used to stay warm in the water, revealing the bathing suit she wore underneath, then picked up her board and started home barefoot through town.

There wasn’t much to Puerto Villamil, which made sense, given that it was one of the most remote towns on earth. It sat on the southern fringe of Isla Isabela in the Galápagos Islands, which were well off the coast of mainland South America. Isla Isabela was actually the largest of the Galápagos, but most of it was uninhabitable, as it was quite volcanic and almost devoid of fresh water. The Sierra Negra volcano constituted much of the island; its crater was the second largest on earth, after Ngorongoro in Africa.

Therefore Puerto Villamil, set at the base of Sierra Negra, was about as far from civilization as one could get. Should a riptide have snapped Charlie away from shore, it was nearly nine thousand miles until she’d see land again. For this reason, it sometimes felt as though the little town was on the very edge of the earth.

That was one of the reasons that Charlie had chosen to come here. She wanted isolation. She wanted to be as far from other people as possible. It was safer that way.

There were more marine iguanas in Puerto Villamil than people. The lizards were quite large, growing up to five feet long, and they were everywhere: lazing on the beach, walking along the dusty streets, lounging on porches, and wandering into the stores. They were just as fearless of humans as they had been back when Charles Darwin had arrived, as was the case with most of the wildlife in the Galápagos. Animals often needed a long time to evolve a healthy fear of humans—and here, there hadn’t been enough. As Charlie headed through town, two sea lions were sleeping directly in the middle of the street, while three penguins waddled toward the small marina. Many people were surprised to learn there were penguins in the Galápagos, as opposed to Antarctica, but this species was endemic to the islands. It was endangered, with only 1,500 left, although they were relatively common on Isla Isabela. One of the things that Charlie liked the best about the Galápagos, in addition to its remoteness, was that it was the only place on earth where you could snorkel with an iguana, a sea lion, and a penguin all at once.

The roar of outboard motors suddenly cut through the town. They were loud enough to startle the penguins, which scurried away frantically, although the sea lions continued snoring loudly. Charlie paused in the street and looked back toward the dock at the eastern edge of Puerto Villamil.

A speedboat had rounded the southern tip of the island and was headed toward town. It was big for a speedboat, with two enormous engines attached to the stern, and it skimmed across the water like a skipped stone.

In the four weeks that Charlie had been in Puerto Villamil, she had never seen a boat like this. Every day, a few boats bringing ecotourists would arrive, but those were all small cruise ships, built for comfort rather than speed. Some of the local fishermen had boats as well, but those were all old, battered, and weather-beaten. This boat was very different; It was expensive and built to go at very high speeds, the sort of craft you’d see millionaires racing along the coast in Miami or the Côte D’Azur in France.

That didn’t necessarily mean anything was wrong, but Charlie was always on the lookout for things that were out of the ordinary. When you lived your life on the run, you had to stay attuned to your surroundings at all times.

Charlie resumed walking toward her home. She didn’t run, because that would draw attention. But she did pick up her pace, striding briskly through the town.

The house Charlie rented was small and ramshackle—there really wasn’t anything big or well built in Puerto Villamil—but she didn’t need much. It sat beside the marsh that marked the western boundary of town. Just behind the house, a path snaked through the wetlands to the Tupiza Tortoise Breeding Center, where Charlie volunteered her time, helping to keep the celebrated Galápagos tortoises from going extinct.

A woman she had never met before was on her porch.

Charlie noticed her from two blocks away. It wasn’t hard, as the woman apparently wanted to be seen. She was sitting in the rocking chair on the porch, reading a book.

She wasn’t from Puerto Villamil. Charlie could recognize every one of the town’s residents. The woman had unusually slim features: her face, nose, and lips were all narrow lines, although her eyes were wide and round. She reminded Charlie of a Modigliani sculpture. She was dressed in the same outfit that the volunteers at Tupiza wore: khaki shirt and shorts, although instead of dusty, thick-soled work boots, she wore running shoes. Despite the workmanlike clothing, she was strikingly beautiful.

A visitor was also an unusual occurrence; Charlie had never had one since arriving in Puerto Villamil. None of her friends or family knew she was here—and ideally, her enemies didn’t either. Combined with the arrival of the speedboat, the visitor’s presence set Charlie’s brain humming, analyzing the probabilities of all that was happening. She didn’t like what she came up with.

Still, Charlie didn’t run. She had nowhere to run to. And the woman didn’t seem to be a threat. Threatening people tended to ambush you. They didn’t sit on your front porch in broad daylight.

As Charlie got closer, she noticed that the woman was wearing makeup. Not much, just a bit of eyeshadow and lipstick, but most people around here didn’t bother with makeup at all. The woman had also spent time doing her hair, and her clothes were spotless and expertly pressed. All of it indicated that this was a woman who cared about how she presented herself.

She looked up as Charlie approached, dog-eared a page of her book, and smiled pleasantly. “Hello, Mariposa. My name is Esmerelda Castle.” There was a slight accent to her words, as if English was not her first language.

Charlie’s immediate response was to pretend as though she couldn’t speak English at all. Any time a tourist had approached her over the past few weeks, she had quickly said “No hablo inglés” and walked away. But Esmerelda seemed very well aware that Charlie understood English, so Charlie figured there was no point in acting like she didn’t. “Hi,” she said, propping her surfboard against the wall of her house.

“I work at the Darwin Research Station on Isla Santa Cruz,” Esmerelda said. “We’ve found something of great interest there, and my friends at Tupiza suggested you might be able to help us with it.”

“Who at Tupiza?” Charlie asked suspiciously.

Esmerelda smiled again, as though she found Charlie’s suspicions amusing. “Everyone, really. Raoul Cabazon. Stacy Devillers. Arturo and Fred and Johnny. They all say that you have a gift for codes and puzzles and that sort of thing.”

Charlie nodded. There didn’t seem to be any point in denying this. The names Esmerelda had mentioned were all people who worked at Tupiza, and Charlie often solved puzzles during her breaks there. Crosswords, cryptics, acrostics, and that sort of thing. She was addicted to them. And what Esmerelda was talking about struck her as strange but intriguing. “You found a puzzle at the research station?”

“Yes. A code of some sort, we believe. It was etched into the shell of a tortoise.”

Charlie’s eyes widened in surprise. “Who would etch a code into the shell of a tortoise?”

“That’s where this gets really interesting,” Esmerelda replied. “It appears the code was left by Charles Darwin himself. And we could use your help figuring it out.”

Reading Group Guide

Reading Group Guide for

Charlie Thorne and the Lost City

By Stuart Gibbs

About the Book
Charlie Thorne is a genius. Charlie Thorne is a fugitive. Charlie Thorne isn’t even thirteen. After saving the world, Charlie is ready to take it easy in the Galápagos Islands. That is, until she’s approached by the mysterious Esmeralda Castle, who has a code she knows only Charlie can decipher. In 1835, Charles Darwin diverted his ship’s journey so he could spend ten months in South America on a secret solo expedition. When he returned, he carried a treasure that inspired both awe and terror in his crew. Afterward, it vanished, but Darwin left a trail of clues behind for those brave and clever enough to search for it. In a daring adventure that takes her across South America, Charlie must crack Darwin’s two-hundred-year-old clues to track down his mysterious discovery. However, when an ancient hidden treasure is at stake, people will do anything to find it first. Is Charlie smart enough to know who she can trust?

Discussion Questions

The following questions may be utilized throughout the study of Charlie Thorne and the Lost City as reflective writing prompts, or alternatively, they can be used as targeted questions for class discussion and reflection.

1. In the book’s prologue, readers learn that Robert FitzRoy, the captain of the HMS Beagle, is ready to abandon Darwin; Darwin has repeatedly delayed the ship’s departure from Ecuador without providing an appropriate rationale for doing so. Darwin finally tells FitzRoy, “‘I saw many incredible things on my journey . . . they all paled compared to this. Everything I have ever encountered in my life pales compared to this.’” In what ways does the opening scene set the stage for the events to follow? Explain your answer using examples from the book.

2. Given his behavior in the prologue, why does Darwin go to such great lengths to keep the lost city and the missing link from being discovered? How do you feel about Darwin’s decisions? Explain your answers.

3. As a large hammerhead shark swims under her surfboard, Charlie is filled with excitement rather than fear. What can you infer about Charlie based on her reaction? Describe other scenes throughout the book that support your conclusion.

4. Part one, “The Edge of the Earth,” opens with the following Darwin quote: “Nothing can be more improving to a young naturalist than a journey in distant countries.” What do you think Darwin means by this? In what ways can this be seen as a call to action? Explain your answers.

5. Though she works hard to remain inconspicuous in Puerto Villamil, Charlie had “already become legendary among the few who lived there. Even surfers with decades of experience mistimed a wave on occasion, but Charlie never did. Somehow, she was always exactly where she needed to be.” Why does Charlie’s ability ultimately cause her to be in danger?

6. Charlie speaks “over a dozen languages and could understand many more.” In what ways does Charlie’s affinity for languages work in her favor? Do you know any words in any of the languages she speaks?

7. Puerto Villamil, on the southern fringe of Isla Isabela in the Galápagos Islands, is about as far from civilization as one can get. Why do you think feeling that she’s on “the very edge of the earth” appeals to Charlie? In what ways does isolation offer her a sense of security?

8. Charlie was “always on the lookout for things that were out of the ordinary. When you lived your life on the run, you had to stay attuned to your surroundings at all times.” What are some of the challenges and benefits to Charlie’s lifestyle? Do you think she enjoys living the way she does? Explain your answers.

9. CIA Director Jamilla Carter realized that “finding Charlie Thorne was of paramount importance to the CIA. And they needed to find her before anyone else did.” Consider the CIA’s motivations: Do you believe they have Charlie’s best interests at heart? Based on what you’ve learned about her, what makes Charlie a great asset to the CIA? Explain your answers using examples from the book.

10. Darwin’s carvings on the tortoise suggest he has knowledge of “the greatest treasure in human history.” How do you interpret his statement? Share your ideas of what the word “treasure” means to you.

11. After Charlie deciphers Darwin’s code, Esmerelda tells her, “‘Apparently, I came to the right person. You figured that out immediately when an entire team of scientists couldn’t do it in two days!’” Why is Esmerelda so surprised that Charlie has been able to accomplish this? Do you think her reaction is typical or atypical to the responses Charlie usually receives for her work?

12. How does Charlie misjudge Esmerelda? What does this reveal about Charlie?

13. Describe Charlie based on what you’ve learned about her in Charlie Thorne and the Lost City. Are there any new traits you’ve learned about her character that surprise you?

14. As they begin to travel down the Amazon, Charlie asks Milana, “‘What have you been up to since betraying my trust a few months ago?’” What can you infer from their exchange?

15. Charlie believes that what they have uncovered in the Amazon needs to remain secret. Do you agree or disagree with her evaluation? What do you predict the outcome would be if the knowledge did get out?

16. Ivan Spetz, the Russian agent after Charlie, is a formidable foe in many ways. What makes him so dangerous? Are there any ways in which he and Charlie are actually alike? Explain your answers using examples from the book.

17. Readers learn more about ecotourism efforts in the Amazon as well as the Galápagos Islands. In what ways do such opportunities support these destinations? Are there any drawbacks you can think of?

18. As they’re being attacked by a seaplane, Charlie devises a plan, telling Dante, “‘I don’t have time to explain everything!’” He retorts by saying, “‘It’s too dangerous.’” Why is he so confident that he knows what’s best for Charlie? Do you agree or disagree with this belief? Based on their interactions in Charlie Thorne and the Lost City, what can you glean about Charlie’s relationship with her brother? How does it continue to change?

19. What do you think about Milana Moon, given all you’ve learned about her in Charlie Thorne and the Lost City? Are there ways in which Charlie’s relationship with Milana is changing as they spend more time together? Explain your answers using examples from the book.

20. Charlie’s participation in this mission takes her around the world; besides the new places she sees, what do you think are the most important things she discovers along the way?

21. In the epilogue, readers learn that “Charlie had learned it was pointless to lie low on the fringes of civilization and hope that no one found her. Ivan Spetz had tracked her down, and there would certainly be more people like Ivan. So it made sense to keep moving, to never stay in the same place for long. That wasn’t necessarily an easy life, but it was certainly less boring than spending the rest of her years in the boonies. The earth was a big planet, and there were plenty of amazing places to see.” Reflect on Charlie’s outlook for her future: What do you think of her attitude and approach? What would you do if you were in her position?

22. Considering the book’s conclusion, what do you predict Charlie’s next adventure will be?

Extension Activities

1. In Charlie Thorne and the Lost City, maintaining secrecy around the discovery of Darwin’s missing link is a major fictional plot point. Read “What is the missing link?” at LiveScience ( to better gain a better understanding of the term. Next, utilize your library’s resources to further research this evolutionary theory. Taking what you’ve learned, engage in a classroom discussion where you share what you’ve found to be most interesting about your new knowledge. What other information about Darwin or evolution would you like to know?

2. Early in the book, readers learn about a tortoise whose shell is carved with a message from Darwin; this makes the creature likely two hundred years old. Learn more about how the ages of animals are regularly determined by reading this guide to aging animals from National Geographic: After reading, talk as a small group about what’ve you learned. Did anyone have questions that were left unanswered? Come up with a plan to work together to discover the answers to any outstanding questions.

3. In the book’s prologue, readers observe Darwin returning to the HMS Beagle in Ecuador after forcing the crew to wait for him as he engages in a mysterious mission. Research to discover more about Darwin’s time on the HMS Beagle, being sure to learn more about the following:

When did Darwin’s HMS Beagle journey take place, and where did it take him and the crew?

Who were the other important figures on board besides Darwin?

How was the voyage documented?

What were some of the voyage’s primary accomplishments?

What were the journey’s greatest challenges or obstacles?

After examining what you’ve learned, engage in a classroom discussion about Darwin’s actions and analyze the outcomes.

4. Charles Darwin is often considered to be the most influential scientist and naturalist of the nineteenth century. Using resources from the library and the internet, investigate his life and work, being sure to look closely at the following:

When and where did Darwin live?

What was his educational background?

What were his most important scientific contributions?

What were his goals as a naturalist?

How did his contributions reshape the world?

What other facts did you find most interesting?

After conducting your research, create and share a digital artifact that synthesizes the highlights of your findings.

5. Charlie’s mission to uncover Darwin’s secrets takes her on a number of grand adventures. Working in a small group, create a map of Charlie’s whereabouts that includes all the locations she visits. Calculate the distances she travels from point to point, as well as an estimated length of time the journey takes her. If you could take a similar trip, would you? Upon completion, pair up with another group and compare and contrast your findings. Then engage in a discussion about embarking on a similar adventure. What do you think you’d learn about yourselves?

6. Charlie’s quest for answers lands her in the Amazon, where readers are introduced to the Amazon River, the second longest river in the world. Use your school’s library or the internet to learn more about the great Amazon, being sure to consider the following:

Where is the Amazon River located?

How long is it?

What animals live near or in the Amazon River?

What makes navigating the river particularly challenging or dangerous?

What are some of the reasons the Amazon River is famous?

Why is the Amazon and the land surrounding it in need of protection?

What are some simple conservation efforts you can make to help care for it?

After completing your research, share your new knowledge with your classmates. Then brainstorm how best to share information about protection and conservation with the rest of your school or community.

7. At the beginning of the novel, readers discover that Charlie has been hiding in the Galápagos to protect herself. Research more about the Galápagos Islands, being sure to focus on the following:

Where are the islands located?

Why are they considered so important?

What is Darwin’s connection to this area?

What are the unique types of wildlife found there?

What are the most important conservation efforts happening there?

What makes those efforts challenging?

After discovering answers to these questions, discuss your findings with your class. Next, talk about your own town or state. Are there wildlife areas in your community that need to be protected? Are there conservation efforts taking place? How might you help?

This guide was created by Dr. Rose Brock, an assistant professor at Sam Houston State University. Dr. Brock holds a Ph.D. in Library Science, specializing in children’s and young adult literature.

This guide has been provided by Simon & Schuster for classroom, library, and reading group use. It may be reproduced in its entirety or excerpted for these purposes. For more Simon & Schuster guides and classroom materials, please visit or

About The Author

Photograph by Dashiell Gibbs

Stuart Gibbs is the New York Times bestselling author of the Charlie Thorne series, FunJungle series, Moon Base Alpha series, Once Upon a Tim series, and Spy School series. He has written screenplays, worked on a whole bunch of animated films, developed TV shows, been a newspaper columnist, and researched capybaras (the world’s largest rodents). Stuart lives with his family in Los Angeles. You can learn more about what he’s up to at

Product Details

  • Publisher: Simon & Schuster Books for Young Readers (March 8, 2022)
  • Length: 416 pages
  • ISBN13: 9781534443822
  • Ages: 10 - 99

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