Enigma(1983)
Submitted by Spectre
Alex (Martin Sheen) has been entrusted to steal a descrambler device from the Russians so an encoded message detailing the murder of five dissidents on Christmas Day can be decoded and the targets saved. Unbeknownst to him however, his operation has been compromised on purpose by the CIA. They already have a descrambler key, and need him to attempt to steal it, so the Russians don’t realize they already got one.
Alex reunites with a past lover, Karen (Brigette Fossey) who agrees to help him, and who ultimately seduces Dimitri (Sam Neill), the young KGB agent tasked to bring Alex down. Though Alex steals the descrambler, Dimitri realizes Alex plans to smuggle it out in a piece of art and recovers it. Confronting the two at the train station, Dimitri ultimately lets the two escape due to the genuine feelings he had for Karen.
Thinking they had won, the Russians transmit the orders for the assassinations. The CIA, who had the means to decode the message, are able to prevent the killings.