The three friends go on vacation with the camper. First time in the countryside! Everything is going well until… Muffin, who has grown up indoors, discovers that their human forgot to bring his litter box. And then he decides to find one in the forest! Together with Snoopy, they go on an exploration, but things go from bad to worse when they accidentally fall into the river. Will Cookie manage to save them so they can all return home together?