The Spy Who Came Out Of The Night

Published in Ellery Queen Mystery Magazine (US - Apr. 1967), then later in the Argosy - The Short Story Magazine (UK - Dec. 1973).
Rand is sent to Berne to help Professor Trenton, an agent from a friendly European power, intercept and decode a message. The message is believed to contain the location and time of a meeting between Constantine Blakov, a Russian agent, and Lin Ching, a Chinese espionage chief, regarding a large sum of money being delivered to Russian agents