NOTE: Sequel to "Dracula A.D. 1972" (1972)
An undercover agent named Hanson (Maurice O'Connell) barely escapes from the Pellham House of Psychic Examination after being tortured. He loosens his bonds and strangles a guard, but trips an alarm when he leaves the building. Armed motorcyclists give chase, but Hanson manages to stagger to the main gate where men in a waiting car retrieve him. At headquarters he tells his handlers of witnessing a satanic ritual in which a naked girl was sacrificed on an altar while five of the biggest businessmen involved in government secrets attended as supplicants. He identifies four of them before he dies -- General Freebourne (Lockwood West), Lord Carradine (Patrick Barr), Dr John Porter (RIchard Mathews) and Professor Julian Keeley (Freddie Jones). His hidden camera has caught them at the facility, though the fifth picture has nobody in it. Figuring black magic is involved, Inspector Murray [Michael Coles] consults occult expert Professor Lorrimer Van Helsing [Peter Cushing]. The professor discovers that Keeley, an old friend and Nobel Prize winner for humanity in science, has turned to satanic worship and has been working on a radioactively accelerated strain of bubonic plague which spreads by touch and kills rapidly. Unfortunately, Van Helsing's visit with Keeley is interrupted by an assailant who shoots and wounds Van Helsing and hangs Keeley.
Inspector Murray, Van Helsing's granddaugter Jessica [Joanna Lumley], and Peter Torrence [William Franklyn] go to Pellham House where they discover a cache of female vampires in the basement. Dr Van Helsing puts two and two together. The Keeley Foundation is funded by the Denham Corporation, run by one D.D. Denham who is never seen publicly and who controls his empire from a building recently erected at St. Bartolph's church, the very spot where Van Helsing killed Dracula two years ago (as in the previous film). If that isn't enough, it is also the day before November 23rd, the Sabbat of the Undead, the night the undead cause unspeakable horrors on earth. Something has to be done. Van Helsing fashions a silver bullet from a cross, goes to the chairman's suite at the office building and confronts D.D. Denham [Christopher Lee], who he confirms is Dracula, but henchmen capture Van Helsing and he misfires the silver bullet.
Meanwhile, Dracula has ordered the capture of Jessica and Murray. His plan is to make Jessica his consort and then to wipe humans off the earth with his new strain of plague. He hypnotizes one of the four executives into infecting himself with the plague and watches, smiling in triumph, as the man suffers excruciatingly horrible symptoms in rapid succession.
As Dracula performs a ceremony over Jessica's body, in another upstairs room Murray is fighting with a guard. The guard is electrocuted, starting a fire and, in the melee, Murray saves Jessica while Dracula and Van Helsing escape the flames through a window. Dracula follows Van Helsing into the woods and the vampire expert lures Dracula to a hawthorn bush, where he becomes trapped, and Van Helsing stakes him with a fencepost. As Dracula turns to dust, Pelham House burns, and along with it burns the bacillus.