Modesty Blaise and Willie Garvin are in Paris. Modesty is invited to dinner by René Vaubois, head of the Deuxième Bureau (the French Intelligence Service), on a floating restaurant on the Seine. René asks Modesty for advice regarding a case. High-level people worldwide are receiving death threats, and those who don't pay a ransom end up dead. Most of the deaths are revealed to be natural.

Willie, waiting on the river bank for Modesty's return, encounters Chuli, a criminal whose speciality is planting bombs. Vaubois' car has been wired with explosives. When Modesty, Willie, Vaubois, and Stephen Collier leave the scene, they are followed by a car full of underworld killers, trying to take down Vaubois.

Lucifer, a young man with a ruined mind who had been studying to go into the church when he was seduced by a woman and suffered a nervous breakdown, becoming convinced that he was the source of all sin, the devil himself. A pair of aging puppeteers, Seff and Regina, unable to get work when the music halls closed down, turned to crime. After discovering Lucifer's ability to predict natural deaths, Seff has created a worldwide protection racket.

Modesty is taken prisoner at their base on Sylt and a radio-controlled cyanide capsule is surgically implanted under her skin. The final confrontation takes place on a remote island in the Philippines. Modesty and Willie are forced to fight a duel to the death against each other. Later in a major battle, Modesty risks everything to try to save Lucifer.