Winter 1169. Isolde arrives at the stronghold of the Descendants, her immortal kin. It soon becomes clear that Isolde is magically gifted, but as she learns to harness her abilities, visions of death and fire consume her.

Heartbroken at parting from young warrior Cuan, and scarred by the destructive power of her enemies the Fomorians, Isolde struggles to find her place in the immortals' world.

Cuan, nephew to the High King, is growing in fame. Caught between a curse that will destroy him, a desire for revenge, and his love for Isolde, Cuan is offered a new path by a mysterious stranger.

But a warrior so close to the king has many enemies, and with Isolde no longer at his side, escaping death a second time may prove impossible.

As war between Ireland's kingdoms continues, Anglo-Norman lords, eager for power, encroach ever further onto Irish soil. Ireland's clans must choose: work, and fight, together - or risk the destruction of their whole world.