Tweed - star detective turned spymaster - reluctantly agrees to make inquiries into a man called Michael Volkanian at the urging of his old friend, Superintendent Buchanan. Buchanan had found Michael on the steps in Whitehall, where he heard him utter only three words: 'I witnessed murder.' With Paula Grey, Tweed embarks on his investigation and gradually locates four skeletons. Two of them are found on Dartmoor, near the mansion of Drago Volkanian, the Armenian founder of a giant supermarket chain - and an armaments plant. Tweed interrogates Volkanian's stepdaughter, the steely and moody Lucinda, her elder brother Larry, the company managing director, and meets Michael again, the youngest sibling, who is still unable to speak. He is suffering from amnesia - or so say two psychiatrists. Unlike Buchanan, Tweed insists that the horrific murders are not random. A link must exist between the four victims. He also suspects that a foreign power is involved. With Paula, Bob Newman and his team, Tweed travels south to Marseilles, where murder is a way of life. Escaping the city alive by a hairsbreadth, they race back to Britain, to desolate Dartmoor. One eerie climax follows another. But who is the ruthless killer? And could Michael be the key to the conundrum?