Two shunned Irish immigrants in Scotland start off as grave robbers to sell the dead to doctors, but decide that creating their own inventory is much easier, and become the most prolific mass-murdering duo in history.

In the German hinterlands, between World Wars, a family goes to bed, not knowing that their killer has been living in the walls and attics of their home like a ghost, watching, waiting for his chance to strike, in one of the most famous unsolved mysteries of all time.