It's in the Bag

Published in the collection The Lives of Harry Lime - novelization of episode 30 of the radio program of the same name as the collection.
Traveling on the Orient Express heading to Belgrade, Harry Lime is becoming more and more annoyed with his compartment mate, Stathacopoulos, but not so much as to do anything about him until he can relieve the Greek of the man's $10k in black market proceeds.