Just before Christmas, the annual 200-meter swim takes place at the swimming hall. Half of Valleby has gathered to witness the highlight of the event: the famous diver Racke Bolinder. However, during his final jump, his swimsuit suddenly slips down because someone has cut the elastic band. At the same time, a fire alarm goes off. Once the initial excitement subsides, the swimmers realize that all valuables from the lockers have disappeared. Lasse and Maja investigate.