Ida Joner gets on her brand-new bike and sets off to buy sweets. A good-natured, happy girl, she is looking forward to her tenth birthday. Thirty-five minutes after Ida should have come home, Helga Joner, her mother, starts to worry. She phones the shop and various friends, but no one has seen her daughter. As the family goes out looking for Ida, Helga's worst nightmare becomes reality, and they contact the police.

Hundreds of volunteers comb the neighbourhood, but there are no traces of Ida or her bike. As the relatives reach breaking point and the media frenzy begins, Inspector Sejer is calm and reassuring. But he finds the case puzzling. Usually missing children are found within forty-eight hours. Ida Joner seems to have vanished without a trace.