Biggles Fails to Return by W. E. Johns
Biggles goes on a secret mission to rescue a Princess from Monaco and doesn't return. Algy, Bertie and Ginger, knowing nothing of his secret mission, find out about this when they go to quiz Air Commodore Raymond. The last known information about Biggles' whereabouts was that he was shot whilst fighting a rear-guard action to allow the Princess to board a plane. This rear-guard action is the event that is depicted on the dust cover of the book. Algy, Bertie and Ginger ask for, and get, permission to go after him. With the help of Henri Ducoste, a local who is fighting with the free French, Biggles' three friends parachute into Southern France and then split up in the hunt for Biggles.