The story draws on Celtic mythology and includes the realm of Faery and the fay race of the Sídhe.

They bargain with Caith, who ends up losing everything he has, including Dathuil, in exchange for their help in overthrowing Sliabhin and freeing Brian.

Caith and Dubhain, alternating between a black horse and a boy, set off for Dun Mhor.

Meanwhile, Cinnfhail's son, Raghallach, rides to the Sidhe-wood to find and assist Caith, but is stopped by Nuallan.

At Dun Mhor, Caith and Dubhain are let in and taken to Sliabhin, who shows them Raghallach, captured and tortured.

The chains holding Raghallach suddenly fall away and Nuallan escapes with Brian, leaving Caith to confront Sliabhin.