SON OF FRANKENSTEIN is generally venerated as one of the best Universal Frankenstein films that followed in the wake of director James Whale's first two classic takes on the Mary Shelley story.. At the same time, it's also the first film in the series to begin the tendency to donwplay the Frankenstein Monster himself as a vital character in the stories. The central characters, much like their writers, treat the Monster as nothing more than a means to an end. One might take this development as a backhanded compliment to James Whale. Perhaps Whale and his assorted writers did such a superlative job of imbuing the creature not just with "life" but with characterization and dimension that every succeeding writer on the Monster didn't even try to play in Whale's ballpark.
Indeed, in re-watching Boris Karloff's last performance as the Monster, I had the strong sense that he as an actor had run out of things to "say" about his classic character, even though Rowland Lee and writer Wyllis Cooper allowed the actor to return the Monster to speechlessness (thus undoing Whale's "education of a
young monster" trope from BRIDE OF FRANKENSTEIN). Karloff gives a solid performance as always, but even if his character had received more screen time, it's questionable that he could have added much more to his conception of the raging yet fundamentally helpless child-monster.
The bulk of the screen-time goes to the warped genius who revives the Monster and the evil being who controls the creature's incredible power-- both of whom care nothing about the Monster's welfare. The latter, the lovably nasty Ygor (Bela Lugosi in one of his best performances), only wants to use the Monster as a catspaw who will kill his old enemies (continuing an idea touched upon in BRIDE OF FRANKENSTEIN, where the scientist's assistant gets the Monster to do some dirty work). The former-- the original mad scientist's titular son, or at least one of them-- is Wolf Frankenstein, who barely knew his late father but has been traumatized by the long shadow cast by his father's deadly deeds. When he discovers that the Monster has survived the explosion at the end of BRIDE and that his friend Ygor wants Wolf to make the artificial creation well, Wolf talks himself into revivifying the Monster with the notion that he can redeem his father's reputation for horror.
Naturally this particular good intention paves the way to a lot more horror, and not least because the creature has become less of a patched-together dead man and more of a cosmic dynamo. Cooper and Lee evidently decided that the only way the Monster could have survived the holocaust of BRIDE was if he became a veritable powerhouse. The old Galvanic explanation alluded to in Mary Shelley's book was clearly no good for this purpose, so Wolf theorizes that Henry Frankenstein actually tapped into the "cosmic rays" which gave rise to life itself, thus causing the Monster to become virtually invulnerable. Oddly, this is accomplished by the fact that even the Monster's blood cells are continually at war with one another. This condition sounds like it ought to make the creature weaker, not stronger, but perhaps the effect the writers were going for was the idea of the Monster as an incarnation of pure violence. Certainly the Monster's character falls in line with this, as he now hates pretty much everyone except Ygor. The creature's one moment of tenderness-- alluded to but not seen-- concern his faltering attempts to befriend Wolf's naive little boy. Yet when Wolf kills Ygor in self-defense, the Monster quite fiendishly plans to kill the little boy in revenge-- though to be sure, one is never completely sure he'll do it.
Wolf's wife and a few other functionaries have largely thankless spear-carrier roles, but Lionel Atwill seems to have as much fun with the role of Inspector Krogh as Lugosi does with evil Ygor, As a child Krogh lost an arm to the Monster during one of the latter's rampages, with the result that he's among the first to become suspicious when the new Baron Frankenstein seems to be conducting experiments in his castle. There's a lovely moment where Wolf's boy mentions how a friendly "giant" grabbed him by the arm; Krogh starts and touches the wooden arm he wears in place of his lost limb..
As Wolf Rathbone does his best to evoke the same sort of hysterical mania that Colin Clive gave to audiences in the previous FRANKENSTEIN films. However, I never felt that Rathbone-- known primarily for roles of smooth persuaders or intellectual paragons (like Sherlock Holmes)-- quite managed to make Wolf come alive, even though the script gives him a lot of material with which to work. The central problem may be that while both the novel FRANKENSTEIN and the two Whale adaptations could delve into psychological depths with the original Frankenstein-- for whom the Monster is both a "son" and the shadow of his other self-- the fraternal conflict between Wolf and his inhuman "brother" never dives quite as deeply.