A very hardworking but also very naive insurance company clerk, Valentin Plavec, becomes the target of endless pranks, jokes and recessions from his colleagues Bejšovec and Voborník. However, their last successful trick somewhat gets out of hand. They add a one to the winning number 8456 and convince Valentin that he has won a million in the lottery. However, since Valentin cannot collect his winnings immediately, he withdraws twenty thousand, which is all the savings he has saved together with his fiancée Helena, and starts shopping for a deposit. However, the truth soon comes out and when his colleagues reveal to him that it was just a joke, they all leave him, only the faithful Helena stays and even helps the unfortunate fiancé cancel all the deposits and agreed deals. When the newspaper reports that there has been a mistake and the winning ticket is number 18456, Valentin decides to take revenge on the two pranksters...