The Coven Murders opens with a horrifying account of a ritual Black Mass with a human sacrifice in an abandoned church. Twenty-one years later, near an old ruined church in an area of outstanding natural beauty, Chief Inspector Sheehan and his team discover the skeleton of a young woman. But what seems initially to be a straightforward case, brings the team into conflict with a powerful Satanist who has plans to offer up to Satan another human sacrifice on the evening of the great Illuminati feast of Lughnasa. Several murders occur, baffling the Inspector until he makes a connection between the modern murders and the twenty-one year old skeleton. The team's pursuit of the murderer, and their determination to protect a young woman who is targeted by the coven, lead to a horrific climax in a hellish underground crypt where Sheehan and his team, supported by an exorcist and a bishop, attempt to do battle with the coven and a powerful demon of Baphomet, jeopardising not only their lives, but risking the wrath of Satan upon their immortal souls.