Overview: Ruth Vang lives in an old appartment building in downtown Oslo. One morning she comes running out of her appartment, falls in the stairs and lies there unconscious. Two neighbours, Vigdis Myrnes and journalist Per Høøk, comes upon the scene and calls for help. In her appartment, they find the body of the owner of the building, Otto Hagenberg. In the appartment building, the married couple Bergheim and the mysterious man Peter Sand, also lives. Helmer and Sigurdson starts the investigation. The journalist Høøk, who is currently working on a case about slum lords, also becomes interested in the case. Høøk wants to help Ruth Vang's son clear his mothers name, and obtains valuable information, which in the end helps Helmer and Sigurdson clear the case and reveal the murderer.