The Dorset Monster was killing people near the town of Dorset. Doctor Christopher Fenn is called in by the local law enforcement to look into the case. Fenn brings his female comanion Wendy along with him. Fenn surmises the creature was invoked by ancient druids to defend against the invading Romans. While performing his investigations, he uses a book called "The Devil's Catalog" to summon three Ghost Roman Soldiers. The ghost Antonius leads the three, one of them named Claudius and the third unidentified.