Two young scientists are exploring new fields of nuclear physics. Dmitry Gusev and Ilya Kulikov are good friends, but rivals in love. Dmitry marries Lyolya and they live happily together. Luck has it that he makes an important discovery. Unfortunately he exposes himself to radioactivity during the experiments. As a result he falls seriously ill. However Dmitry has a strong spirit. His will to live, the deep passion for his work and his strong love for mankind makes it possible for him to recover.
Алексей Баталов
as Dmitri Gusev
Иннокентий Смоктуновский
as Ilya Kulikov
Татьяна Лаврова
as Lyolya
Михаил Козаков
as Valery Ivanovich
Николай Плотников
as Professor Sintsov
Сергей Блинников
as Butov
Евгений Евстигнеев
as Nikolai Ivanovich
Валентин Никулин
as young physicist
Павел Шпрингфельд
as physicist
Люсьена Овчинникова
as Nura, Gusev's younger sister
Андрей Смирнов
as tall bearded physicist
Евгений Тетерин
as Surgeon
