The Adventures of Corporal Kochetkov (1955)

Gunner-gunner Corporal Vasily Kochetkov meets Valya Gradskaya, a saleswoman at the military trade center, and becomes a frequent guest in her family. He soon realizes that the girl and her grandmother are spies. Kochetkov informs the command of his suspicions and is given the task of continuing to play the role of the groom.