Ireland, AD 671. On the eve of Samhain, Eadulf and the warrior Aidan find a stranger dressed as a religieux and killed by the ritual threefold death. A prophetess in a raven-feather cloak claims that the old gods are returning, encouraging fear that the murder marks a pagan challenge to Cashel.
Fidelma discovers that the ritual spectacle is connected to a forbidden book stolen from the papal archives, a text said to threaten Christian belief in the Five Kingdoms. She must determine who is manipulating religious panic and recover the manuscript before the conflict between old and new faiths becomes a weapon against her family.