On a stormy night, the old lighthouse keeper saves the little mouse Eisbjörn. He is allowed to stay with him in the lighthouse, and soon they become thick friends. But one day, Gustav becomes so ill that he cannot light the lamp in the lighthouse in the evening. When a storm arises that very night and a fully loaded ship heads towards the coast, the fate of the sailors rests solely in Eisbjörn's paws! For the little mouse, a race against time begins.