For all the acclaim that Boris Karloff received for playing Frankenstein's monster in three iconic movies, it meant that he was forever associated with the character, and ended up typecast as horror-movie monsters and villains for much of his career (not that he didn't get to play plenty of other roles). So there's a certain poetic justice in seeing him toward the end of his career playing Dr. Frankenstein opposite someone else as the hulking, mute monster, even if the version of Frankenstein in Howard W. Koch's Frankenstein 1970 is still ultimately the villain in a horror movie. Also, Koch is no James Whale, and Frankenstein 1970 (which is not, so far as I can tell, actually set in 1970) is a cheap, mostly worthless B-movie whose only real saving grace is Karloff's dedicated performance.
Karloff plays Victor Frankenstein, descended from the original Frankenstein of the book (who is, confusingly, not named Victor). He lives in a sprawling castle in Germany, where he continues his ancestor's experiments in a secret underground lab. He's also rented out his estate to a film crew from the U.S., and Koch and screenwriter Richard H. Landau come up with some amusing banter for the low-budget filmmakers, whose movie seems to resemble the kind of production they are also starring in. But after an entertaining fake-out opening, the pacing slows to a crawl, padding out the minimal story in order to barely reach feature length. As Frankenstein works on his experiments, the oblivious film crew starts getting picked off one by one, harvested for parts that the doctor needs for his monster. Shot in CinemaScope, the movie makes very poor use of its wide-screen compositions, with numerous scenes featuring characters just standing around at the edges of the frame while someone else talks.
Although the castle has a certain gothic charm, most of the set design is bare-bones, and the lab itself looks notably cheap. The ridiculously tedious action includes numerous scenes of Frankenstein flipping what seems like every single switch in the lab, while narrating in minute detail everything he's doing. Karloff's mellifluous tones make even these excruciatingly dull details seem grandiose and menacing, and he brings a haunted quality to Frankenstein, who was disabled by Nazi torture during World War II. There's some potential thematic richness to the story of a scientist perpetrating the same kind of cruel experiments he virulently opposed when the Nazis committed them, but that thread is quickly dropped in favor of goofy comic relief from the film crew and endless shots of the lumbering, laughable monster.
Wrapped in bandages like a mummy and with a head inexplicably shaped like a bucket, the monster isn't remotely scary, no matter how loudly the female characters scream when he confronts them. Although he supposedly has the brain of Frankenstein's assistant Schutter (and Frankenstein continues to call him by that time), he's just a stumbling automaton with no personality or desires. He does whatever Frankenstein tells him, but the scientist's motives are a bit muddled. Frankenstein doesn't seem to set out to murder everyone, but he takes to it pretty easily, and then gives up nearly as easily once the authorities catch on. After its laborious pace, the movie ends abruptly, with both Frankenstein and the monster succumbing to what is meant to be a tragic end but is just as cheap and silly as the flimsy sets surrounding it.