Peter Tremayne: Valley of the Shadow

From the Publisher:
The year is A.D. 666. Dispatched to the valley of Gleann Geis as an emissary of her brother, the king of Muman, Sister Fidelma has been charged with a formidable task. She must entreat the chieftain of a Druid clan to allow the construction of a Christian church and school in the region.

But before entering the valley, Fidelma and Brother Eadulf find the slaughtered bodies of thirty-three young men - covered in scars from an ancient pagan ritual. As advocate of the Brehon law courts, Fidelma must learn who or what is behind the shocking massacre - before it threatens the peace of her brother's kingdom...

Peter Tremayne: Valley of the Shadow. Signet, ISBN: 0451203305 (July, 2001), 320 p., $6.99.