Pettersson and Findus are celebrating Findus's birthday, which they've already had three times this year. Findus remembers arriving in a box, so they decide to celebrate the day he was found. Even the chickens are excited. Pettersson agrees to make his famous pancake cake but cannot find the flour, and his bicycle has a flat tire, so he cannot buy more. When they finally gather everything for the cake, their neighbor Gustavson arrives with news: the fox has been spotted and he plans to catch the chicken thief soon. Pettersson and Findus believe the fox should not be shot but merely scared. The story follows whether their plan will succeed in driving the fox away.