Prelude for War is a mystery novel by Leslie Charteris featuring his Robin Hood-inspired crime fighter, Simon Templar, alias "The Saint".

A peaceful moonlight drive in the English countryside is interrupted when Simon Templar and Patricia Holm listen to a disturbing radio broadcast from France by a would-be dictator who plans to make it the latest in a growing number of European dictatorships under a ruling party, the Sons of France.

This broadcast disturbs Patricia, and Templar makes a dire (and, as it will turn out, accurate) prediction that the future of Europe will be one of invasions and concentration camps.

Now firmly intrigued, Templar continues his investigations, which lead him on the trail of an assassination plot designed to spark a Second World War, a clue to which is provided from beyond the grave.

The book's cover indicates this plot element, portraying the Saint as trying to close a door through which armed soldiers are trying to enter.