First light, Ascension morning. From the top of the tower at the College of Transfiguration, voices rise in song. Felicity's delight turns to horror when a black-robed body hurtles over the precipice and lands at her feet. Her fiancé Father Antony recognizes the corpse as Hwyl Pendry, a former student, who has been serving as Deliverance Minister in a Welsh diocese. The police, ignoring the strange emblem of a double-headed snake clutched in the dead man's hand, label the death as suicide. But Hwyl's widow is convinced otherwise, and please for Felicity and Antony to help her uncover the truth. Matters grow murkier as Felicity and Antony, leading a youth pilgrimage through rural Wales, encounter the same sinister symbol as they travel. Lurking figures following them. Then a body is found face-down in a well....