Dead Letter Drop by Peter James
Featuring a special introduction by Peter James, Dead Letter Drop is Peter James' first ever novel, originally published in 1981.
Max Flynn, undercover agent, has the unenviable job of spying on his own side. When to kill, who to kill, whether to kill are all questions which have to be answered at great speed if he wants to stay alive.
But why does an innocuous airline ticket No. 14B matter so much? Who has gone to the trouble of committing suicide? And could Flynn's beautiful companion be a spy? The hazy, murky world of counter espionage leaves no room for errors of judgement and Flynn knows he's finished if he makes one false move.