A film adaptation of a popular Norwegian book about the adventures of Svein and his rat, Halvorsen. An action-packed and adventure-filled story about the fact that it is worth counting on the help of friends tackling difficulties, problems and prejudices together, even when they are only of concern to ... a rat.
Seven-year-old Svein and his rat, Halvorsen, are inseparable. Svein wants Halvorsen to take part in a pet competition organized every year. But not everyone is convinced this is a good idea. They claim that an ordinary rat shouldn’t compete with dogs and cats. As if that were not enough, Halvorsen is constantly causing trouble—at least that’s how Svein’s parents see it. He runs away, causes mischief and thus keeps the entire family on their toes. The situation gets even more complicated when panic breaks out at Svein’s school due to a suspected rat invasion. Will Svein manage to convince the adults that Halvorsen is not a threat and that he deserves to take part in the competition? His classmates come to the rescue.