Telefon is a 1977 American action movie about a Soviet KGB agent (Charles Bronson) who is sent to America to stop a rogue Russian from activating brainwashed sleeper agents. The film costars Donald Pleasence and Lee Remick.
Nikolai Dalchimsky (Pleasence), a disgruntled KGB office clerk, learns of a long-abandoned Soviet plan to place sleeper agents in the United States who would then be in position to sabotage key installations at the start of a war between the two countries. To preserve their covers, the agents are brainwashed into believing that they are Americans, and can only be activated by using a trigger phrase (a line from the Robert Frost poem "Stopping By Woods on a Snowy Evening.") Dalchimsky steals a copy of the book listing the names and locations of the agents and heads to America to begin activating them; he calls them one by one and reads the trigger phrase to them over the phone. The sleepers carry out their suicide missions, but many of their once-important targets are now of little military interest.
The KGB summons agent Grigory Bortsov and hastily explain that the old sleeper program was supposed to be terminated; instead the spy agency left the agents in place. To keep the Russian leadership or the Americans from finding out, they order Bortsov to travel to America and kill Dalchimsky.
Bortsov is met in the United States by KGB secret agent Barbara (Remick), and the two chase Dalchimsky across America. Bortsov is puzzled by the seemingly random geographic selection of sleepers until he realizes that Dalchimsky is choosing them by the first letter of their home towns, spelling out his own name in terror attacks. Bortsov and Barbara are able to intercept and deactivate the next sleeper agent, then quietly stage a fatal "accident" for Dalchimsky in a rattlesnake-themed bar.
After Dalchimsky is stopped, Barbara reveals that she is supposed to kill Bortsov to eliminate any loose ends. Instead they both decide to go rogue, informing both the Americans and Soviets that they will trigger more sleepers unless they are left alone.