The Viking King of Dublin is dead. His young widow, Gormflaith, has ambitions for her son - and herself - but Ireland is a dangerous place and kings tend not to stay kings for long. Gormflaith also has a secret.

She is one of the Fomorians, an immortal race who can do fire-magic. She has kept her powers hidden at all costs, for there are other immortals in this world - like the Tuatha De Danann, a race of warriors who are sworn to kill Fomorians. Fodla is one of the Tuatha De Danann with the gift of healing.

Her kind dwell hidden in a fortress, forbidden to live amongst the mortals. Fodla agrees to help her kin by going to spy on Brian Boru, a powerful man who aims to be High King of Ireland. She finds a land on the brink of war - a war she is desperate to stop.

However, preventing the loss of mortal lives is not easy with Ireland in turmoil and the Fomorians now on the rise.