The last of the Hammer Horror Dracula films features a very interesting plot. Picking up where the last movie, Dracula A.D. 1972, which brought Dracula into the modern times.
British secret service have been monitoring a house out in the country. A Satanic Cult has set shop there and even more disturbing several prominent members of society appear to be members. A member of parliament, a secret service officer, a general and a famous scientist.
A secret agent escapes from the house but dies of his wounds. The agent manges to tell his superiors about the members.
To avoid trouble with the suspected members, the secret service enlist Scotland Yard’s Inspector Murray (Michael Coles).
Murray brings Van Helsing (Peter Cushing) and his granddaughter Jessica Van Helsing (Joanna Lumley) onto the case. Meanwhile the cult kidnap a secret service secretary revealing that the cult is run by Dracula (Christopher Lee). Dracula bites the secretary turning her into a vampire.
The Van Helsings and Murray break into the house and find the vampire secretary who they kill. Vam Helsing meets with the scientist and discover that he has been working on a new bubonic plague. This leads him to a businessman named D.D. Denham who is really Dracula.
Dracula plans to release the plague and wipe out humanity.
Hammer films had been huge for a decade but the series was getting pretty weak. Lee hated the deviations from the original source material and this was his last Dracula Hammer film.