Directed by Mikhail Romm • 1962 • Soviet Union

Dmitriy Gusev, a nuclear physicist, receives a dangerously high dose of radiation as a result of an accident in which his professor, Sintsov, is fatally exposed. Warned that another exposure would prove fatal, Dmitriy nevertheless refuses a safer job and continues the experimentation. Lyolya, Dmitriy's girl friend, feels that their relationship means little to him and decides to marry their best friend, theoretician Ilya Kulikov. Learning that Dmitriy's life is in danger, however, she realizes that she loves him, and they marry despite his misgivings. From the outset of the marriage, Dmitriy's singular devotion to his work keeps them apart. At a Siberian research center, Dmitriy works together with Ilya, and though Ilya's cynical manner is so different from his own, their disagreements do nothing to mar their friendship and mutual respect. As a new success is obtained, Dmitriy is again exposed to radiation. He persuades Ilya to keep the accident a secret until the experiments are completed. Lyolya, misunderstanding Dmitriy's remoteness, feels that she has failed as a wife. Dmitriy's health deteriorates, and, aware of his doom, he makes a visit to his family. At a Moscow clinic he asks doctors to perform an experimental bone marrow transplant with little chance of success. Ilya comes to visit him on the day before the operation and tells him that their experiments produced a new type of radiation which was not thermonuclear, as anticipated, but nonetheless would be an important contribution to science. As Ilya and Lyolya await the outcome of the operation at the hospital, they receive a note from Dmitriy promising a celebration.