A man with a sandwich-board (advert) wanders around London meeting many strange characters.
Simon Templar is hired by a friend in the book publishing trade to protect one of his stars, a secretive recluse named Amos Klein who writes a popular (and lucrative) series of adventure novels about a manly and suave spy.
The Cat Gang is a group of precocious British kids. They have a habit of hanging around a grown-up customs official who wishes that they'd beat it. But the Gang comes in handy when a smuggling gang arrives on the scene.
Simon Templar is The Saint, a handsome, sophisticated, debonair, modern-day Robin Hood who recovers ill-gotten wealth and redistributes it to those in need.