Some things are best left buried…
Ireland in the 1590s. Fortune Rochester travels with a small group of soldiers carrying despatches to the isolated fort where her father commands the garrison. They arrive to find the garrison slaughtered and the bodies mutilated. The soldiers believe the local Irish were responsible. But when they explore an ancient Celtic burial mound they discover Fortune’s father, violently insane. One of the soldiers is forced to kill him – and soon afterwards begins to act out of character.
One by one the soldiers are horribly killed – but by who? Realising there is something amiss, Fortune tries to leave the fort, only to be fired upon by the local Irish, who are determined to quarantine everyone in the fort.
When the soldiers capture a young Irish Chieftain, O’Donnell, Fortune learns about the Morrigan, an ancient female demon which had been imprisoned in the burial mound for centuries – until Fortune’s father set it free. The Morrigan is a war demon, and feeds on the energy of violent conflict. The soldiers scoff at the story – but helped by O’Donnell, Fortune works out that the demon had possessed her father, and leapt into his killer at the moment of death. She discovers the awful truth – whoever kills the person possessed, will themselves become possessed. As the Morrigan picks off the soldiers, one by one, Fortune and O’Donnell work together to find a way to overcome the demon, and somehow lock it back beneath the earth.