South Devon is returning to its usual calm after the summer tourist season when DI Wesley Peterson and his team receive a disturbing call. A mummified body has been discovered, hidden behind a wall, during the renovation of nearby Sycamore House.

The body is that of Dr Aleric Donnal, an academic with a special interest in Devon's medieval history. Donnal was last seen over a decade ago, around the time that Sycamore House belonged to a new age commune who believed that the house occupied an ancient sacred site. While Wesley is seeking potential suspects for Donnal's murder, his friend Dr Neil Watson is investigating the ruins of an ancient chapel nearby; a building once decorated with grotesque carvings of mythical creatures.

As Wesley's team work on one of their most baffling cases yet, a new murder occurs in a nearby village. Could the two crimes be linked? Wesley needs to separate truth from myth in order to solve this mystery.