Ireland, AD 666. A headless woman is discovered in the well of a remote coastal abbey, holding a Christian cross while a pagan death symbol is bound to her arm. On the journey to investigate, Fidelma also encounters an abandoned Gaulish merchant vessel whose crew and cargo have disappeared.
The unidentified corpse, the missing sailors and tensions within the religious community initially appear to be separate mysteries. Fidelma must establish the woman's identity and follow evidence moving between land and sea, revealing a scheme whose consequences could disturb the peace of Muman and endanger Eadulf himself.