When senior Russian official Gen. Marenkov decides to defect to the West, CIA agent Harry Wargrave is sent to lead the team to get him out. Malenkov reveals that the Russians are trying to develop biological weapons. Wargrave decides that Malenkov should travel across Europe by train, on the "Atlantic Express", in an attempt to lure the Russians into attacking the train so that they can discover who the Russian secret agents in Europe are. During the journey they must survive a terrorist attack and an avalanche, all planned by Russian spy-catcher Nikolai Bunin. A tape gets decoded and Harry hands it over when he boards the jet plane with Elsa.