Janek and Wanda live in a small room in a villa, while other rooms are occupied by offices of various institutions. Janek often stays at work after hours, just to avoid returning to the cramped apartment too early. One day, a man named Malinowski, who once lived in the same small room, visits the couple. He proposes to exchange their room for a new, two-room apartment that he has just received. Janek and Wanda are initially distrustful, but eventually, the exchange takes place. It turns out that Wanda's ex-husband, Jerzy, already lives in the new apartment. Despite the divorce, as he is registered with Wanda, he has the right to continue living in her apartment. Janek tries to find a way to get rid of the intruder.