Johanna Bischoff is a music teacher. When she comes to visit Hamelin, her hometown, with a girls‘ choir, she finds herself staying for a few days in the house where she grew up, with her father Georg, the former mayor, and his sister Charlotte, who was like a mother to little Johanna. But suddenly she is tormented by a terrible vision – of herself as a little girl with a dead man.
Just before the concert that has been scheduled for the choir, four of the girls and Johanna's boyfriend David go missing while out walking on Ithberg Mountain - the legendary area where the rat-catcher is supposed to have led the children of the town 700 years ago. In desperation Johanna turns for help to her ex-boyfriend Jan Faber, now a senior officer with the local police. A feverish search for David and the missing girls begins, with officers combing the forests and caves of the mountain.
Johanna is gradually forced to the realisation that the mystery of David and the girls is inextricably bound up with a tragic tale – the story of her own family.