Student Petr neglects his school attendance. In order to get an apology for missed lectures he starts to work at a construction site. He says to his colleagues that he had to interrupt his studies in order to make money for his sick mother. The workers call him a bit derisively an engineer. One day he meets a young student of economy and he invites her to his home. The girl likes him and so she does not mind that he is not any engineer. But Petr gets drunk and the girl leaves in the end crying. At work the foreman prepares a charge for an earth blast. But the charge doesn't blast. The sulky workers and the foreman go for lunch, only Petr is on sentinel. Petr tries to deactivate the charge but it explodes. Petr is severely injured. He is ashamed for his imprudence and irresponsibility. Therefore he refuses to see his mother, his girlfriend and his colleagues who come to visit him in the hospital. Eventually he thinks everything over and he asks the doctor to invite them all in his room.