The story of a man who plans the perfect crime. He murders his wife while they are on holiday together in Norway. Two children see the wife falling into the deep waters of the fjord with a heavy camera bag tied round her. The children go to the police, but there is no hope that the body will be found. However, one of the children has a film which was in the camera bag, and there is a little piece of blue wool in the bushes below the path. Gradually the children piece the evidence together, but will they be able to catch up with the murderer?