Ida Joner gets on her brand-new bike and sets off toward town. A good-natured, happy girl, she is looking forward to her tenth birthday. Thirty-five minutes after she should have come home, her mother starts to worry. Hundreds of volunteers comb the neighborhood, but there is no sign of Ida or her bike. Amid the media frenzy, Inspector Konrad Sejer is calm and reassuring. But he does find the case puzzling. Usually missing children are found within forty-eight hours. Ida Joner seems to have vanished without a trace.