Singer Dan Sampson and his wife Theodora suddenly divorce after twenty years of happy marriage for no apparent reason, leaving Theodora devastated and his friends mystified. Three months later Dan has married another woman, Morgan, who is the opposite of Theodora in almost every way. In their new home in England, they have employed a housekeeper called Medb. Medb appears to have a strange relationship with Dan and Morgan, and is the subject of terrible nightmares for Theodora and some of Dan's friends. Together they try to find out who-or what-Medb is, suspecting she is connected to Morgan, an admitted magician. However, they don't realize that Dan has a secret past of his own.