Promenade mixer Willy travels to Munich by train as a stowaway. On the way, he meets little Natalie and makes friends with the girl. When he arrives in Munich, Willy is not only hungry but also has to read about a dangerous gang of dog catchers. Willy is happy when he meets Natalie again and is allowed to come home with her. However, Lord, his new girlfriend's distinguished pedigree dog, makes life difficult for him there. When Lord is caught by the dog catchers, Willy doesn't hesitate for a second to help him. In the end, the brave mongrel falls into the clutches of the criminals himself.