Blue Flags, the first in the Flag series of novels, introduces Philip Marlin, a nineteen-year-old engineer cadet serving in the British merchant navy. On a voyage from the United Kingdom to the Far East on the motor vessel Olympus, Marlin becomes unwittingly and dangerously exposed to a scheme to steal a bag of gem grade diamonds from a passenger. ¿But who actually stole the diamonds and will they get away with it?