Baron Frankenstein seeks refuge in a new town with a new identity. He stays at a boarding house but when he finds out that the landlady's fiancé is stealing drugs from the local asylum, he blackmails them into helping him with his new experiments.
When he find out than an old colleague of his is locked inside the local asylum and has gone mad, Frankenstein comes up with a crazy idea to transplant his brain into a new body and conduct some brain surgery to cure his madness. But after the success of the operation, Frankenstein realises his old friend was mad to begin with and the monster hunts Frankenstein down for a fight to the death.
Whereas the Hammer Dracula franchise seemed to run out of ideas quickly, their counterpart Frankenstein series continued to churn out strong, creative films. Yes each film was basically the same "Frankenstein creates monster, monster gets loose, etc" plot but in each installment, a new element was added and over the course of Cushing's Frankenstein films, you can clearly identify the progression of the character as the scripts gave him fresh challenges. The studio could quite easily have rested their laurels and regurgitated the same story over and over again but each film took the idea of Frankenstein's experiments in different directions. It's this continuity and evolution of the character which sets the Frankenstein series head and shoulders above the Dracula films, helped in no small part by Peter Cushing.
By the late 60s, the public was so well-acquainted with Cushing as Frankenstein that the films didn't to feature the 'trademark' monster as the last film, Frankenstein Created Woman, so aptly proved. Frankenstein Must Be Destroyed does feature a monster but it's not the typical brute we've come to expect from the 'Frankenstein' name. This time the monster is in the shape of actor Freddie Jones who retains most of his former human side, going so far as to return to his home to confront his wife who then proceeds to reject him as his brain now has a new body which she refuses to accept. It's a pitiful, heartbreaking moment but one which embodies the new direction that the monster was taken with this entry. A monster in all but character tag, this near-man has only a visible scar around his skull to give away his past. The monster is simply a tragic character and not depicted as the usual lumbering zombified hulking mass - certainly one of the most complex incarnations of the monster ever seen on film.
But the monster is only one small part of what makes this film such a great horror film. Terence Fisher brings to life some nightmarish sequences including the classic burst water mains moment which reveals a disembodied hand. Frankenstein Must Be Destroyed also cannily plays upon previous Frankenstein films by ending inside a burning building. There's a great opening sequence in which Frankenstein makes sure that he isn't going to be burgled again by eliminating the problem. And don't think you'll get through a Hammer film without some trademark blood either and with brain surgery being on the menu, you'll get to see a brain transplant taking place. It's one of Hammer's most enduring and controversial scenes which looks tame nowadays but caused uproar back in the day.
As good as the supporting players are, this is Cushing's show from the get-go and to talk about anyone else would not do this performance justice. Always a master of making even the most rudimentary horror films seem like classy genre pieces, Cushing was always at his best when the material he had to work with was just as good. This time Frankenstein is more manipulative, more deceitful, more calculating and more murderous than ever before. He will let nothing and no one stand in his way and is prepared to go to any lengths to achieve his goal. What was once single-minded determination is now an obsession. By attempting to prove that everyone else is mad for not believing in him, Frankenstein has now become borderline insane.
Once misguided, Frankenstein is now evil. He'll go through anyone and everyone to achieve his goal and that includes rape and murder. The rape scene is a tad unnecessary and a bit out of character, even for Hammer (legend has it that Cushing, being the respectable gentleman he was, even apologized to the actress whilst shooting the scene). It cheapens the film and is a blot on its otherwise almost-impeccable landscape. But during the bits where Frankenstein is required to blackmail, Cushing looks so icy and cold that you'd never believe him to be a nice guy. He could have sleepwalked through the role at this point in time but continued to drive further forward, pushing the character for all it's worth.
In a film laced with classic Cushing moments, the standout is when he cuts down his fellow physicians inside his drawing room. Scathing and brutally brilliant, it shows both Frankenstein at his most sinister and Cushing at his ever-best. No matter how low he stoops to achieve his goal, he still manages to gain the admiration of the viewer through his natural charisma. We actually want to see him succeed in his work even if we don't agree with his methods - real bastard of an anti-hero if ever there was one.
Frankenstein Must Be Destroyed is one of the best of the Hammer Frankenstein films and certainly one of the best films they ever made. It would be unfair to lavish all of the praise upon Cushing's performance as Frankenstein since the script, the direction and the supporting players are all as equally on top of their game. But it is an intense, compelling portrayal which would likely get a token Oscar nod nowadays. An absolute must-see horror film.