As William Jones digs in the garden of his council house he finds a strange looking stone head. During the night his wife has horrible dreams, forcing William to move the head out of the house. In turn, he takes the head to an archaeologist at Bangor University who is an expert on Celtic artefacts and trying to dig up the remains of the Celts elsewhere. In order to try and understand the head, he goes home with her but things start to go wrong at night there as well, bringing the horrors of a half-human half-animal creature to the housewives. One by one the archaeologist's family is horrified leading to death and another sacrifice to the ancient gods of the Celts.

Documentary about Thomas Edwards, better known as Yr Hwntw Mawr, a murderer and the last murderer to be publicly hanged in Merionethshire.