In the first of the Lemmy Caution series

A group of organised gangsters are operating a ''snatch'' racket, laying a plan — worked out in the minutest detail — to kidnap the daughter of an American millionaire while she is in England.

And their plot must not only account for the actual luring of the victim into the snare and the collection of the ransom money, but also evade interference from the English police and rival gangs.