Based on the memoirs of Igor Gouzenko and directed by William Wellman, a Russian officer works with ciphers in the Soviet embassy in Canada and decides to defect.
In 1943 code expert Igor Gouzenko (Dana Andrews) arrives at the Soviet embassy in Ottawa, and Col. Ilya Ranov (Stefan Schnabel) orders him to do his work secretly without making any friends. Secretary Nina Karanova (June Havoc) tries to seduce him, but Gouzenko tells her that he loves his wife. Soviet agents manage to recruit Canadians such as Member of Parliament Leonard Leitz, Captain Donald P. Class, and nuclear scientist Dr. Harold Preston Norman (Nicholas Joy) to give them secret information especially on nuclear weapons. They work closely with the local founder of the Communist Party John Grubb who is known as agent “Paul.” (Berry Kroeger).
Gouzenko’s wife Anna (Gene Tierney) arrives, and the Gouzenkos are happy to have a three-room apartment. He warns her not to let their friendly neighbor Mrs. Albert Foster (Edna Best) visit their home. Anna becomes pregnant and after attending a Soviet meeting tells her husband of her misgivings about the fear imposed on them. Gouzenko is called to the embassy to work and there learns that his wife gave birth to a son. He is concerned about what sort of life his son will have and is influenced by the doubts and complaints of the drinking Major Semyon Kulin (Eduard Franz). While drunk, Kulin criticizes Soviet policies so much that he is put under arrest and ordered to go back to Russia.
Soon after the end of the World War II Gouzenko is told that he is being sent back to Russia as soon as he trains his replacement. He tells his wife, and they plan to escape. He steals several important documents by smuggling them under his shirt. He tries to give them to Canada’s Minister of Justice but is told to come back tomorrow. In the morning he does not report to work and is not allowed to meet with the Minister. So he goes to a newspaper office, but the city editor thinks he is a crank. Gouzenko, Anna, and the baby return to their apartment to pack. When the Soviet officials arrive at the apartment, Gouzenko sends Anna and the baby to the friendly neighbor’s apartment. The officials break in, and Ranov interrogates Gouzenko who refuses to give him information. Anna arrives with two Royal Canadian Mounted Policemen. Ranov says Gouzenko is a deserter, and they want to take him back to Russia. Gouzenko sends his wife next door to get the secret papers, and then he gives them to the police and explains what those documents are. Ranov says he stole them from the embassy. The policeman says stolen items must be claimed at the police station. The Gouzenkos realize they are safe as the police take them into protective custody. The Soviets go back to Russia, and several Canadians who helped them spy are tried and sent to prison for several years.
This true story changes only a few minor details to increase the drama which naturally has great propaganda value for the western powers. The story is presented in a fairly realistic way, though the Communists are portrayed in negative ways. The film is a significant depiction of a seminal event that has been considered by some to mark the beginning of the Cold War.