It is Halloween, and something isn't right in Nottingham Castle. Allan A Dale, in attendance as Guy of Gisborne's right-hand man, is startled when a mysterious illness begins to spread amongst the servants - an illness that appears to involve the desire to consume human blood... Suddenly, he finds himself in a race against time to stop the transmission of the virus. Is the Sheriff a vampire? And will Robin Hood, Allan's sworn enemy, agree to help him defeat the bloodsuckers?