Little Kati lives with her mother Anna in a tiny apartment. The two of them are struggling to make ends meet by singing at the Christmas market. When Anna is once again late with the rent, her heartless landlord throws her out just before Christmas. Fortunately, Willy Wuff has heard about their misfortune and rushes to help. He puts them up in the villa of millionaire Jakob, who is on a winter vacation with his mistress. However, when he breaks off the vacation in an argument and returns home, he realizes who has taken up residence in his house. And Kati and her mother mistake the intruder for a burglar. The beginning of a series of amusing mix-ups.