Findus is feeling bored and wishes to celebrate his birthday again. However, they have already celebrated it three times this year. Then, Findus recalls that he arrived at Pettersson's house in a box, leading them to the idea of celebrating a Findus-in-a-box birthday! The chickens are thrilled, and Pettersson agrees, even promising to make his famous pancake cake. Yet, he can't find the flour and can't buy more because his bicycle has a flat tire, and the key to the carpenter's shed is missing.

As they finally gather everything needed for the cake, their neighbor Gustavson arrives with bad news: a fox has been sighted again. The neighbor wants to deal with the chicken thief soon. However, Pettersson and Findus argue that shooting the fox isn't necessary; scaring it away should suffice. But will their plan actually scare the fox off?