Randi Wallace, an American graduate student, travels to England to study under Dr. Ian Matheson, a noted British professor specializing in mythology. Matheson urges Wallace to do her own, so Randi heads for the countryside, where she is brutally attacked on the moors under a full moon, by a large animal. Randi recovers from her wounds only to discover that she turns into a werewolf during the next full moon, destroying her office and nearly killing Ian to boot. Returning to the moors, Randi and Ian meet a band of gypsies who react strangely when shown a piece of ...
Ian's aunt uncovers a well-preserved corpse from a bog on her property and asks the professor to ride to her village and determine its antiquity. Before he arrives, his aunt is brutality murdered and soon other villager are found slain, each in the manner of their profession. Randi is convinced that a blind old man with a drinking problem may have valuable information on the case that the authorities are ignoring.
Randi and Ian learn of another scientist conducting research into lycanthropy from a woman who claims her brother sought treatment after being bitten by a werewolf. Randi is committed to the mental asylum were the research is conducted and finds the doctor is experimenting on his hapless patients to develop a serum to create more werewolves.
Julian takes an interest in the new girl in class, Liza Parfrey, whose father recently prevented a coven from practicing pagan services in his church. When Liza begins to see ghosts in the church, the vicarage and the cemetery, she turns to Randi and Ian for help. Ian believes that the coven may have raised The Juggler, an evil clown who preys on the children of their enemies and warns Julian to stay close to Liza during the Guy Fawkes Day celebration.
An elderly man who claims to be only 27 years old answers Ian and Randi's newspaper advertisement and begs for their help. While their client recovers from a heart attack Randi investigates and suspects that a succubus is on the loose in London, sucking the youth out of her victims. Randi captures the being, but not before the succubus has attacked Ian prematurely aging him by 50 years.
Randi and Ian investigate when they learn that two prominent publishers were murdered by normal people dressed as characters in the classic novels recently delivered by an antiquarian bookshop. The bookstore owner acknowledges that he cast a spell on the books to punish the men and women he considers responsible for driving him nearly to bankruptcy and confides to Ian that he has sent a truckload of the cursed books to members of Parliament since they passed the laws enabling chain stores to gobble up independent bookshops.
Ian is ecstatic when a Hollywood movie company asks to convert his latest book into a movie until he discovers their representative is Randi's former fiancé who appears to be more interested rekindling his relationship with the lovely coed than negotiating a production deal with the professor. Meanwhile, Ian and Randi investigate reports of zombies rising from the grave seeking human flesh.
Randi returns to England to battle Samantha Stevens who intends to collect the three lightning bolts of Gilgamesh so she can rule the dead. When Ianand the other zombies try to steal the last bolt from the British museum, Randi initially manages to thwart their attack but is captured and bound to an altar to serve as a human sacrifice so Samantha can complete her deadly ritual.
On a weekend getaway, Ian's car breaks down in an blighted town without connection to the outside world by vehicle or phone. Randy witnesses a sword-wielding horseman behead a young man who asked for her help, and learns that the town is cursed by The Huntsman, a warlock who rides through the town slaying whoever he has marked for death. When a mysterious rune made with blood appears on Randi's hotel room door, the townspeople are reluctant to help them leave town for fear of The Huntsman's reprisal.
Ian's attempts to convince Dr. Mason, his mentor and a famous Oxford mythology professor, to recommend him for a job at the famed university are sidetracked when ghosts inhabit the bodies of Ian's parents - one desperate to pass over to the other side on the 100th anniversary of her death and the other who will do anything to prevent it - including killing Dr. Mason.
Randi feels strangely attracted to the Caleb Wakefield, the ringmaster of a rundown circus. The attraction deepens when she discovers that she does not metamorphose into a werewolf when she spends the night of a full moon with him. Randi learns that Caleb has a steep price for this 'gift' - all she has to do to be permanently rid herself of the curse is to sell her soul to the Devil.