One mild summer evening Lily and her husband are enjoying a meal while their baby daughter sleeps peacefully in her pram beneath a maple tree. But when Lily steps outside she is paralysed with terror. The child is bathed in blood.

Inspector Sejer is called to the hospital to meet the family. Mercifully the baby is unharmed, but her parents are deeply shaken. Sejer 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. From his living room window, the inspector watches a figure slip across the car park and disappear into the darkness. Inside the envelope Sejer finds a postcard bearing a short message. Hell begins now.