Twelve-year-old Nonny Feuerberg's father is the world's greatest detective, wholly dedicated to the war on crime. Nonny aspires to follow in his father's footsteps but, to his father's dismay, his wild side keeps breaking out. Then all of a sudden Nonny finds himself traveling on a train with the magnetic, elegant Felix Glick, international outlaw extraordinaire.

Not until Felix has hijacked the locomotive and whisked Nonny off on a quest for the trademark purple scarf of the great actress Lola Ciperola does Nonny realize that he is in the hands of a kindly and fascinating kidnapper - and that, though he himself knows almost nothing about his own mother, who died when he was a baby, both Felix and Lola seem to know a lot about her.