In Paris in the year 1845, medical student Pierre Dupin and his roommate Paul take their respective girlfriends Camille L'Espanaye (to whom Pierre is engaged) and Mignette visit a carnival one night, taking the sideshows, when they're drawn to one where the barker boasts of an ape with a human mind. Inside, they and the rest of the customers meet the strange Dr. Mirakle, who introduces them to his ape, Erik, who he claims can speak to them in a language the rest of humanity has "forgotten." Mirakle then promotes Erik as the first human being and when an audience member accuses him of heresy, he vows to prove his theory with his experiments of mixing Erik's blood with that of a human being. Pierre, Camille, and their friends are invited up to get a closer look at the ape, who takes an immediate liking to Camille and grabs her bonnet, viciously attacking Pierre when he tries to get it back for her. After backing Erik away, Mirakle offers to replace Camille's bonnet and asks for her address, only for Pierre to insist that it won't be necessary. When they leave the carnival, however, Mirakle follows them to Camille's flat but doesn't do anything because of Pierre's presence, instead abducting a prostitute to use as an experimental subject. However, when her and Erik's blood are mixed, it doesn't take and she dies from it, forcing Mirakle to dispose of the body by having his servant, Janos, dump it in the river, his third failure during the time he's been in Paris. Meanwhile, Pierre, who's been studying the corpses of the first two victims, bribes the coroner into giving him a sample of the latest one's blood upon seeing the same mark on her arm as the other two and, upon examining it, discovers the same foreign substance found in the bloodstream as well. He then learns of Mirakle's continuing fascination with Camille, as he delivered a new bonnet to her home, meaning he now knows where she lives, and when he visits the doctor at the carnival that night, he's told that they're moving on to Munich... only to overhear outside that Mirakle is staying behind. Continuing his studies, Pierre discovers that the foreign substance is the blood of a gorilla, realizing his worst fears, just as Mirakle has Erik abduct Camille to make use of her in his experiments.
Murders in the Rue Morgue has two major strengths going for it, the first of which is Bela Lugosi, who was one of those actors, who no matter what he was in, gave nothing but his absolute best and this film is no exception. For starters, he has a very distinct look in the film due to that wild hairdo and those big eyebrows, which mesh well with those piercing eyes that he had and he looks quite creepy when he's stalking the dark, fog-riddled streets, looking for would-be test subjects. More importantly, though, he proved that he could play a mad scientist with the best of them, including Colin Clive and Boris Karloff. Dr. Mirakle believes 100% in his work in trying to prove the link between man and ape and nothing, not even kidnapping or his potentially fatal methods, will stop him from succeeding in fusing the blood of a human with that of his ape, Erik, in order to create a mate for him. In fact, by the time he abducts the prostitute early in the film, he's already gone through two other women and is furious with this woman's "rotten blood" that doesn't mix well with Erik's. As maniacal-looking as he is, though, Mirakle is not entirely unsympathetic, as seen when he's clearly horrified upon realizing that the woman has died from the toxic mixture of her blood and Erik's, even appearing to say a prayer, an action that, along with his raving that the girl's blood is "rotten" because of her sinful life, goes against his mockery of the one patron's cries of blasphemy towards his theories. Granted, he has no problem with getting his servant, Janos, to dispose of the body by dumping it in the river like garbage and he probably wouldn't have let the girl go if she had lived since she would have probably gone to the police, but it still shows that he's not a completely soulless monster.
Speaking of Erik, this would probably be a good point to touch on how the filmmakers brought him to life, as it's an interesting mix of techniques. For the wide, full-body shots of him walking around and attacking people, it's obviously a man in a suit (specifically Charles Gemora, who was a veteran of playing apes in film), although it's actually pulled of quite well in that he's often photographed either in shadow, from behind, or in far-off shots. However, for big close-ups of Erik's face when he snarls and roars, they cut to footage of a real ape and even though it's a chimpanzee rather than a gorilla, which is what he's supposed to be, it's still noteworthy because you don't often see that in these old movies, which were usually content to have the costumed performer all brightly-lit for everyone to see. What's especially interesting is how the climactic sequence of Erik carrying the unconscious Camille across the rooftops of Paris feel almost like a lead-in to King Kong, which was released the following year, a fact that wasn't lost on the makers of that Universal Horror documentary as they cut from the close-up of Erik's snarling face as Pierre fires at him to the POV shot of the airplanes swooping at Kong atop the Empire State Building while shooting at him.
If Lugosi is one of the film's biggest strengths, the rest of the cast, unfortunately, is a major weakness, as nobody else comes close to matching the level he brings to it, least of all the young lovers. There is virtually nothing to say about Camille L'Espanaye (Sidney Fox, who's billed above Lugosi in the credits, for some reason), as she's nothing more than the typical damsel in distress who has to be saved from the monster at the end of the movie. She's pretty but doesn't have anything close to a personality and actually thinks both Erik and Mirakle are interesting, not finding the latter sinister until after Pierre has told her about the suspicious actions he's been taking as of late. I also find her voice to be a little bit annoying too with that French accent, especially when it's in a high-pitched state. Her fiancé, Pierre Dubin (Leon Ames, who's credited as Leon Waycoff as that was the name he used during the early years of his career), isn't much better. His scenes with Camille range from fairly cute and sweet to being so corny and schmaltzy that it makes you want to puke, especially when Mirakle first follows them to Camille's home and they're on the balcony, with Pierre going on, "Oh, darling. I love you so much." Bleh, gag me with a spoon! And while you'd think his examinations the victims' bodies would be for his studies as a medical student, it seems to be more of some morbid fascination given his roommate, Paul's, line, "If you'd pay have as much attention to your studies as you do to this nonsense, what grade's you'd get." We all know what the reason behind his fascination with the ghoulish case is: the film needs somebody to discover what Mirakle is up to so they can save the lead girl in time and even that doesn't come without some difficulties, as Pierre is almost arrested for the death of Camille's mother that Erik caused when he abducted her for knowing too much for his own good and having to use a tuft of the ape's hair clutched in the woman's hand as evidence that his farfetched claims are true.
One other person who do find to be a little bit memorable is Pierre's friend and roommate, Paul (Bert Roach), whom you see in the opening scene enjoying the carnival with his own girlfriend, Mignette (Edna Marion), although he enjoys the belly-dancers a little too much for her as she becomes very jealous at his comments about them and gets smacked across the cheek for them. The scene with him that I find to be the most memorable is the one where he's acting more like a frustrated, neglected housewife than a roommate, going on about how Pierre spends so much time studying the blood samples he gets from the corpses that he doesn't eat, drink, or even say anything, suggesting that he might as well go live in the morgue and instead of making one out of "our home," and saying that he had to pull bread out of his nose so they could eat after Pierre gave the morgue keeper the money. He's also not that impressed with Mirakle and his theories, calling him a fraud, although he does seem to realize the ramifications when Pierre tells him what he's discovered. However, that's the last we see of Paul, as I don't recall him trying to help Pierre clear his name when he's being charged of murder. After him, the only other cast members I remember are the morgue keeper (D'Arcy Corrigan), who Pierre bribes in letting him take a blood sample from the latest victim, despite the trouble it could cause him should the police find out, and trusts that he's good for the money when it's obvious that he doesn't have the bulk of it on him at the moment, and Mirakle's loyal servant, Janos (Noble Johnson, who I thought for the longest time was an African-American but, as it turns out, played all sorts of ethnicities in his career), who obeys his master without any questions and tries to hold back the mob at the end when Mirakle is trying to complete his experiments.
After Lugosi, the other major strength that the film has is its look and production design, which is German Expression to a 'T.' Created by Charles D. Hall and Herman Rosse, both of whom had worked on Dracula and Frankenstein and the former of whom would go on to work with James Whale on The Invisible Man and Bride of Frankenstein, as well as on Edgar G. Ulmer's The Black Cat (the first film to star both Lugosi and Boris Karloff), the sets are very evocative of what you saw in those films, particularly The Cabinet of Dr. Caligari in the way the buildings are designed in a kind of off-putting manner, especially the rooftops that Erik scrambles across while carrying Camille in the climax (a sequence that is inspired by that film in and of itself). Indeed, for the most part, the environments are made to look uncomfortable, be they Mirakle's rather crude-looking laboratory where he conducts his experiments while keeping Erik in a nearby cage and tying his subjects to a rack (which looks very similar to the rack that Lugosi's Werdegast ties Karloff's Poelzig to in order to skin him alive at the end of The Black Cat), the confined, shabby-looking tent where he exhibits Erik, the poor-looking apartment that Pierre and Paul share, the very depressing, dark morgue that has a very dank feel to it as well, and the dark, often fog-riddled streets of Paris, lit only by the gaslights. Really, the only locations that are a little more inviting are the carnival itself, the flat Camille shares with her mother (which is still made to look very moody when Mirakle has Erik sneak into the place to abduct Camille), and the picnic Pierre takes Camille to, which is by far the most brightly-lit, warm scene in the whole film; otherwise, 19th century Paris is portrayed as a very unsettling place for anyone unfortunate enough to live there.
The film's cinematography is courtesy of another veteran of classic horror, Karl Freund, who'd photographed notable German films like The Golem and Fritz Lang's Metropolis and had also done the cinematography for Dracula. Like the art direction, his lighting and photography gives the movie is a definite feeling of Expressionism, with lots of darkness and shadows, most notably in the scene where Erik abducts Camille from her bed at night, with plenty of shots of his shadow on the wall and it falling over the sleeping Camille as he prepares to strike, and when you see the shadow of the prostitute tied to the rack in Mirakle's laboratory as he prepares to take a blood sample. Speaking of which, the scene where Mirakle abducts her off the street is a very moody scene, with thick, white fog everywhere, giving a classic, Victorian-era horror feel to it (I really like the image of the gaslight surrounded by the mist), and Mirakle looks very creepy as he steps out of the shadows towards her, with barely any light on him until you see the close-up of his face as he asks, "A lady... in distress?" Another bit of photography that I like are the close-ups of the dead prostitute's hanging feet as Janos chops off the ropes holding her to the rack, ultimately dumping her down a trapdoor to the river below, and there are other noteworthy shots like how the camera swings back and forth with Camille as Pierre pushes her on one at the picnic, the shadowy shot of her passed out on her bed after seeing Erik in her room, and the discovery of her mother's body stuffed up the chimney after she's been taken.
As impressive as Lugosi and the technical aspects are, though, the film is very weak in many other places. Besides the supporting cast being pretty bland and forgettable, there are times where the pacing drags, despite the movie's only being 60 minutes long. The most egregious examples are the picnic sequence, which begins with a crowd of people waiting for Camille outside her window, proceeding to break into song which she joins them in, and goes into an overly long montage of people who I don't know or care about having fun at the picnic until we finally get back to the story when Camille tells Pierre that Mirakle sent her a new bonnet, and the police investigation of Camille's disappearance and her mother's murder. The worst part of the latter is when the police prefect interviews three witnesses of different nationalities, an Italian (Agostino Bogato), a German (Herman Bing), and a Dane (Torben Meyer), who tell him that they heard Camille scream and the sound of someone speaking a language other than English (never mind that everyone should really be speaking French) whose origin they can't agree on. This leads into a long argument between the three, who being yelling at each other in various languages to try to prove their individual points, and it's obviously meant to be comic relief but it does nothing more than grind the story to a complete halt. In addition, there are moments where the film simply isn't as exciting as it should be, mostly because, like a lot of these films, there's little-to-no music score save for the opening and ending credits (the entire opening piece, complete with the lead-in to Swan Lake, which, of course, had been used for the opening of Dracula, would be recycled for the opening of The Mummy that same year), with the one exception being the cheerful music and singing heard during the picnic. Usually, this helps establish mood and, indeed, there are moments here where that is the case but there are others where, when combined with the very sparse soundtrack and slow editing, it makes the film a little boring. For example, before Mirakle abducts the prostitute, there are two men fighting over her who end up killing each other but it's not nearly as exciting as it sounds due to the lack of anything kinetic (I know it's stupid to expect anything like that from a movie made at this time but there are peers of it that I can get into a whole lot more). The same goes for the climax of Erik scrambling across the rooftops with Camille as a mob chases after him: it's just not as exciting as it should be and definitely doesn't have the energy that the climactic chase of Frankenstein had.