As they are preparing to return to Ireland, Fidelma and Brother Eadulf receive a mysterious summons. Eadulf's childhood friend, Brother Botulf, has requested their presence at Aldred's Abbey at midnight on the old pagan feast of Yule. Fidelma and Eadulf battle against the harsh winter storms to arrive in time, only to find they are too late. Botulf is dead - killed by an unknown hand. As they struggle to comprehend this staggering news, it soon becomes clear that the murder of this young monk is not the only trouble facing the abbey. The abbey is haunted by the ghost of a young woman - a woman some say bears a startling likeness to the Abbot Cild's dead wife. But can Fidelma and Eadulf discover the truth before they themselves fall victim to the danger which pervades the abbey walls?