Rose Elliot, a poetess living in New York City, purchases a book from a local antiques dealer. Written by an alchemist known as Varelli, the book explains how the author was commissioned by three evil (and very powerful) witches to construct stately mansions for them, from which they rule over the world with insanity, grief and despair. Realizing that the apartment she now resides in might be the home of Mater Tenebrarum, the Mother of Darkness, Rose writes to her brother Mark, currently studying music in Rome, to warn him of her fears.
Mark returns to New York, and finds that Rose has vanished. Taking up residence in her apartment, Mark tries to piece together the whereabouts of his sister, only to discover that her initial fears were horribly correct.
The second film in a loose trilogy (between Suspiria and Mother of Tears), in terms of storytelling Inferno is the most alien of the three. While Suspiria walked a thin line between murder mystery and surreal horror, Inferno dispenses with any sort of narrative structure, instead running on a dream logic that makes no concessions to reality.
This film provides examples of:
- Alien Geometries: The far out architecture of Rose's apartment (to say nothing of the Tanz Akademie or the Palazzo Varelli) makes more sense when you realize it was designed by a medieval alchemist.
- Asshole Victim: Kazanian who drowned a few cats out of annoyance and ended up being eaten by rats and stabbed to death for knowing too much. Also Carol who was in cahoots with the coven if not a member herself and ended up burned to death.
- Big Bad: Mater Tenebrarum who is disguised as the nurse
- The Butler Did It: Subverted, though it's implied not for lack of trying.
- Call-Back: When the apartment building begins to burn, Mater Tenebrarum cryptically says it's happening "Just like before." This may refer to the destruction of the Tanz Akademie in Suspiria (1977).
- Cats Are Mean: Easily one of the most unintentionally hilarious examples ever comitted to film.
- The Cruella: Kazanian, although considering events earlier in the film, he may be somewhat justified.
- Decoy Protagonist: Several.
- Early-Bird Cameo: Mater Lachrymarum, who serves as the main antagonist in Mother of Tears, makes a brief appearance in this film, although played by a different actress.
- Eaten Alive: Kazanian by rats.
- Encyclopedia Exposita: The Three Mothers, by E. Varelli.
- The Faceless: In contrast to Suspiria, where the entire faculty belongs to the coven, the faces of Tenebrarum's coven and servants are appropriately masked by shadow at all times.
- Failure Hero: Unlike Suzy in Suspiria, Mark had done nothing to contribute to the villains's defeat. Tenebrarum died in the fire that she had unintentionally caused on her own through one of her murders.
- Gainax Ending: More "Gainax Entire Film." Between the insane colors and architecture, good luck figuring out what's happening at any given time. It does, however, look very cool.
- He Knows Too Much: Why Sara, Rose, and Elise are all killed.
- Hell Hotel: Apartment, but the principal is the same.
- The Hecate Sisters: The Three Mothers.
- Laser-Guided Karma: Elise's butler and Carol the caretaker are glad that she is gone because they can steal her belongings. Carol even implies that she knows and is allied with Elise's killers. The butler has his eyes gouged out (but still attached to the nerves), and Carol accidentally starts the fire which destroys the building. In her attempt to put the flames out, she gets tangled in curtains, set on fire, and then stumbles out a window and falls several stories to her death.
- Never Found the Body: Every last death other than Varelli's. This is partly what leads to the titular inferno. It's entirely possible that Mother of Shadows does not die at all, as her guise as Death simply vanishes amid flames.
- Considering the last time we see her she's screaming as her house falls apart around her, it'd be reasonable to assume she died with her house, much like her predecessor.
- Off with His Head!: Subverted. Rose is nearly decapitated by a large pane of glass, only it doesn't completely sever her head from her body. Instead, it's repeatedly slammed into her neck harder and harder, cutting deeper through until she finally dies.
- Pinball Protagonist: Played straight, but arguably proof that Tropes Are Not Bad. Mark survived and may have played a role in the death of Mater Tenebrarum, but even at the end has little more than faint hints as to what happened.
- Pop-Star Composer: Keith Emerson wrote the music.
- Scenery Porn
- Soundtrack Dissonance: Perhaps the best music for sneaking around the Big Bad's lair isn't bombastic Ominous Latin Chanting set to synthesized and up-tempo organ. However, it makes sense in terms of being a key component to support Argento's visual aesthetic.
- Swarm of Rats: Kazanian encounters these after drowning a sackful of cats. Just desserts, perhaps.
- Thematic Series: The second part of the Three Mothers Trilogy with Susperia and Mother of Tears.
- Video Nasty: Was placed on the list in 1984, was dropped just a year later, and was released uncut in 2010.
- Walk on Water: After Kazanian falls into the Central Park Lake and is attacked by rats, a hotdog vendor brandishing a knife runs across the lake and finishes him off.