The Secret Ways — Alistair MacLean

Winters are silent in Budapest, silent and dark, and behind some door is some ancient street Harold Jennings, the brilliant British scientist, sat rehearsing a speech denouncing his own country.

The communists intended to sue Jennings' speech as the propaganda coup of the decade. The British were equally determined that it should never be delivered.

Michael Reynolds, Britain's top agent, was given the impossible assignment -- enter Hungry, kidnap Dr. Jennings and return him to the free world; and this, Reynolds decided, was roughly like trying to find an invisible needle in a burning haystack.