Some four years after the events of The Wolf Man and The Ghost of Frankenstein, two men break into the Talbot family crypt to open the grave of Larry Talbot (Lon Chaney, Jr.), seeking valuables buried with him, on the night of a full moon. During the robbery, the thieves remove the wolfsbane buried with Talbot, and he is awakened from death by the full moon shining on his uncovered body. Talbot reflexively grasps the arm of the grave robber with a fur-covered hand, as the cryptkeeper flees.
Talbot is found by police in Cardiff later in the night, with a vicious head wound (administered by his father at the end of The Wolf Man), and taken to a hospital where he is treated by Dr. Mannering (Patric Knowles). Talbot slowly comes to understand his situation, but during the full moon, he transforms into the Wolf Man and kills a police constable. The next morning, Mannering realizes his patient had been roaming about, and tries to reason with him, though unable to accept Talbot's explanation of his curse. Dr. Mannering allows Inspector Owen (Dennis Hoey), to question Talbot who becomes violently irate, then is overcome by orderlies and bound to his bed with leather straps. Not believing his story of being a werewolf, the doctor and detective travel to the village of Llanwelly to investigate Talbot and his story. While they are away, Talbot escapes from the hospital, by biting through the restraints with his teeth. Seeking a cure for the curse that causes him to transform into a werewolf with every full moon, Talbot leaves Britain and seeks the gypsy woman Maleva (Maria Ouspenskaya), who has hearsay knowledge of Dr.Frankenstein (Ludwig Frankenstein, as the action is returning to the Ghost of Frankenstein locale) and opines he may able to help Talbot. Together they travel to the village of Vasaria, where Talbot hopes to find the notes of Dr. Frankenstein in the remains of the his estate, and permanently end his own life through scientific means. The townsfolk want no part of them or their desire to meet with the deceased Frankenstein and rudely order them to leave.
An upset Talbot transforms into the Wolf Man and howls madly, causing the villagers of Vasaria to raise a mob to chase him down. Fleeing toward the ruins of the Frankenstein manse, Talbot falls through the burned-out flooring and into the frozen cellars below. Talbot recovers from his animal state, and wanders around, discovering Frankenstein's Monster (presumably Bela Lugosi, but actually stuntman Gil Perkins) frozen in ice and thaws him out with a fire. Finding that the Monster is unable to locate the notes of the long-dead doctor, Talbot seeks out Baroness Elsa Frankenstein (Ilona Massey) the daughter of Ludwig, posing as a potential buyer of the estate, hoping she knows their hiding place. She declines to assist Talbot, but the pair are invited to the "Festival of the New Wine" by the Burgomeister (Lionel Atwill).
During the festival, a performance of the life-affirming folk song Faro-la Faro-Li enrages Talbot as Dr. Mannering arrives. The doctor, having followed him across Europe, converses with Talbot to persuade him to return to Wales before he has another spell. Talbot refuses to go with Mannering, and the Monster crashes the festival. With the Monster revealed, Elsa and Mannering agree to help the villagers rid themselves of the Frankenstein curse forever. The following morning, the couple, with Maleva in tow, meet with Talbot and the Monster at the ruins. Mannering is instantly fascinated by the Monster scientifically, and the Baroness gives the notes to Talbot and the doctor. Mannering studies the notes and learns how to drain all life from both Talbot and the Monster, believing the laboratory can be repaired for the task.
In the meantime, the villagers are dismayed to see crates of instruments arriving for Dr. Mannering to enable the experiment and become restless, knowing nothing of the doings at the ruins. Vazec, the innkeeper details a plan to destroy the dam overlooking the old estate with dynamite and drown all within, ending their troubles in one blow. The Burgomeister dismisses the idea as nothing but a drunken notion, but Vazec is determined and puts his plan into action.
Unfortunately, Dr. Mannering's scientific curiosity to see the Monster at full strength overwhelms his logic, and to Elsa's horror he decides to fully revive it. The experiment coincides on the night of a full moon, and Talbot transforms yet again as the Monster regains his strength (and eyesight); both escape their restraints.
The Monster begins to carry Elsa away, but the Wolf Man attacks him, and she escapes from the castle with Mannering. The Wolf Man and the Monster then engage in a fight until they are both swept away in the flood that results when Vazec dynamites the dam.
As ultimately edited and released, Frankenstein Meets the Wolf Man is told in two almost equal parts. The opening scenes tell the story of Talbot's resurrection, killing spree, hospitalization, and escape across Europe. Much time is spent with a secondary policeman, Inspector Owen, and on scenes with a desperate Talbot hospitalized by Dr. Mannering. The discovery of the Monster and pursuit of Dr. Frankenstein's scientific notes do not begin until thirty-five minutes into the film. The second half introduces the Monster, Elsa, and the village of Vasaria and its inhabitants.
Screenwriter Curt Siodmak claimed that during a lunch in the studio commissary he had joked to producer George Waggner that he had a great title for a new film in the series (half-heartedly — he needed a down payment for a new car): "Frankenstein Wolfs The Meat Man". Waggner, not known for a casual sense of humor, left to have his lunch; shortly thereafter, he called Siodmak to his office, telling him to "go ahead, buy the car." Dumbfounded but pleased, the writer went to work; thus that next film was Frankenstein Meets the Wolf Man, which served as a sequel both to The Wolf Man and The Ghost of Frankenstein.
Immediately following his success in Dracula, Bela Lugosi had been the first choice to play the Monster in Universal's original Frankenstein film, but Lugosi famously turned down the nonspeaking, heavily made-up role: as conceived by the original director Robert Florey, the Monster was nothing more than a mindless killing machine and not suitable for Lugosi's rising stardom and career as a leading actor. After the change of directors to James Whale, along with a major script and conceptual revision, the virtually unknown Boris Karloff was then cast in his star-making role. (Florey later wrote that "the Hungarian actor didn't show himself very enthusiastic for the role and didn't want to play it.") Eight years later, Lugosi joined the franchise as the Monster's twisted companion Ygor in Son of Frankenstein. He returned to the role in the sequel, The Ghost of Frankenstein, in which Ygor's brain is implanted into the Monster (now Chaney), causing the creature to take on Lugosi/Ygor's voice. After plans for Chaney to play both the Monster and the Wolf Man in the next film fell through for logistical reasons, the natural next step was for Lugosi, who turned sixty during the film's production, to take on the part that he once was slated to originate.
The original script — and indeed the movie as originally filmed — had the Monster performing dialogue throughout the film, including references to the events of Ghost and indicating that the Monster is now blind (a side-effect of the brain transplant as revealed at the end of the previous film, and the reason for his iconic stiff-armed "Frankenstein Walk"). According to Siodmak, a studio screening audience reacted negatively to this, finding the idea of the Monster speaking with a Hungarian accent unintentionally funny (although the Monster spoke with Lugosi's voice at the end of Ghost of Frankenstein, the audiences had been carefully prepared for it by the plot of the film). This has been generally accepted as the reason virtually all scenes in which Lugosi speaks were deleted (though two brief scenes remain in the film that show Lugosi's mouth moving without sound). All references to his being blind were also eliminated, rendering the Monster's groping gestures unmotivated. Close-ups of Lugosi's eyes during the revitalization scene and his evil, knowing leer to Patric Knowles were supposed to indicate that his vision had been restored, but in the ultimate context of the film this mean nothing. Consequently, Lugosi is onscreen literally for only a few minutes, leaving the Wolf Man as the film's primary focus.
Lugosi suffered exhaustion at some point during the filming, and his absence from the set, combined with his physical limitations at age sixty, required the liberal use of stand-ins. Stuntman Gil Perkins allegedly portrayed the Monster in the character's first scene (thirty-five minutes into the film) and during much of the monsters' fight (conclusive documentation needed). Although a still exists of Lugosi in the ice, when viewers see the Monster for the first time (including closeups), it is actually the stunt double Perkins. Stuntman Eddie Parker is usually credited as Lugosi's sole double, but his primary stunt role was thought to be that of the Wolf Man. However, he does appear as the Monster in at least one shot, and yet a possible third stuntman also stands in for Lugosi in two brief sequences. The edited result unfairly suggests that Lugosi had to be doubled even in non-strenuous scenes, and the multiple use of alternating stuntmen in both closeups and medium shots damages the continuity of Lugosi's characterization. As an example, the doubles in the fight scene stiffen their arms, even though that was a cautious habit of the previously-blind Monster; for instance, a medium shot shows Lugosi pulling down a cabinet with his arms naturally bent at the elbows, but the next shot is of a double completing the task with straightened arms.
This would be the final Universal horror film in which the Monster played a major role; in the subsequent films House of Frankenstein and House of Dracula, the Monster, played by Glenn Strange, is brought back to life only in the final scenes. (In the 1948 Universal comedy Abbott and Costello Meet Frankenstein (the second and final film in which Lugosi plays Dracula), Strange has a larger role and the creature once again speaks, albeit with very limited dialogue, twice muttering, "Yes, Master.") It was also the last Universal horror film to feature an actual member of the Frankenstein family as a character.
Bosley Crowther of The New York Times called the film "a great disappointment" because he thought that the fight between the two monsters came as too little, too late. "Too bad. Not very horrible. Universal will have to try again," he wrote. Other contemporary reviews were more positive. Variety called the film "[e]xpertly contrived, and carrying suspenseful chiller tenor throughout ... Director Roy William Neill deftly paces the film with both movement and suspense to keep audience interest on sustained plane." Harrison's Reports wrote: "For those devotees who like their horror pictures strong, this one will fill the bill ... The action and the eerie atmosphere conforms to a familiar pattern, but it does not detract from the film's horrendous nature." Film Daily called it "a horror feast in which devotees of the weird and the fantastic will gorge themselves to bursting. The opportunities for screams are offered with unparalleled generosity."
Frankenstein Meets the Wolf Man currently holds a 25% approval rating on Rotten Tomatoes.
A tribute to this meeting of two horror film legends happens near the beginning of the film Alien vs. Predator, when this film is seen playing on a television at the satellite receiving station. In the US version of the 1962 film King Kong vs. Godzilla (another pairing of prominent monsters), the music from the fight scene at the end of the film also plays during the final fight between Godzilla and Kong.
The 2009 film House of the Wolf Man is a tribute to Frankenstein Meets the Wolf Man and Universal's other "monster mash" films and also features a climactic clash between Frankenstein's Monster and a werewolf.