Big brother takes a book away from his little sister. She takes revenge by practising her flute while he tries to read. When the fight escalates, brother and sister lose themselves in the vastness of an eerie sea of fog. While searching for his sister, the boy is captured by plundering Vikings. The Vikings let him and their booty be guarded by a gigantic sea serpent while they celebrate their raid. With the help of music the girl frees her brother from captivity and the nightmare comes to an end.