A large construction site brings together Mareto, who had an illegitimate child; Petko, an extramural student and Mantov, whose child is slowly dying of an incurable disease. Mareto and Petko are in love. Apprehensive lest she be abandoned because of the child, Mareto insists that their liaison should remain in a secret. Petko, who knows nothing of the previous affair, misunderstands it and breaks with his girlfriend. Mareto quits the site. Petko, having found out the truth, rushes after her and takes her come back from the railway station. They reunite in Mantov`s home where Mantov and his wife are trying to overcome their anguish for the doomed child and prevent their relationship from falling apart.