On the train to Prague, the bride-to-be Zuzana Vítová accidentally meets the clerk Dr. Karel Jánský. Upon arriving in Prague, it seems that Jánský follows the girl on her way from the station, but it turns out that the two of them have only a common journey. When Zuzana discovers that her fiancé Petr Klika is not at home and that she has lost the keys to his apartment, Dr. Jánský gallantly helps her and keeps her company until deep into the night...