Biggles' Second Case by Capt. W.E. Johns

In Biggles’ Second Case, Biggles, Algy, Ginger, and Bertie hunt down a rogue German submarine, U-517, captained by the ruthless von Schonbeck, carrying a cargo of gold stolen from Allied ships during the Second World War. On their way to recovering the gold they have to depth charge a submarine and escape a firing squad.