One summer evening Lily and her husband are enjoying a meal while their baby daughter sleeps peacefully in her pram beneath a maple tree. But then Lily steps outside to find her baby soaked in blood. The distraught parents rush to the hospital where they discover that she is unharmed. Inspector Sejer is called in and spends the evening trying to comprehend why anyone would carry out such a sinister prank. Then, just before midnight, somebody rings his doorbell. The corridor is empty, but the caller has left a small grey envelope on the mat. Inside it, Sejer finds a postcard bearing a short message: Hell begins now...