Like its predecessor, Mordum is presented as a degraded home movie shot by serial killers. This one includes the returning character Peter, his sadomasochistic girlfriend Crusty, and depraved man-child brother Maggot. What has happened with Peter's accomplice from the first part is left unexplained.
After Peter walks in on Crusty and Maggot having sex, an argument erupts between him and Crusty, but it is quelled when Crusty sexually arouses Peter and herself via self-mutilation with a piece of glass. The two then break into a crack house, where Peter beats the owner to death with a hammer, while Crusty films the filth-encrusted building and the decaying corpse of an overdosed addict. When Peter starts stripping the body of the house's owner (claiming it will be easier to dispose of without clothes), another fight breaks out between him and Crusty when she questions his motive for undressing the body, accusing him of being "a faggot."
The film then switches to a scene of Crusty demonstrating her love of self-harm to Maggot and a friend, cutting her scarred arm with a knife. Crusty and Maggot are then shown removing a bound and masked woman from a box they have been keeping her in for "a long time." Maggot rapes the woman while Crusty cheers him on and taunts the victim. When Maggot is finished, he then lets a male captive out of another box, and he and Crusty force him to perform a penectomy on himself with a pair of cuticle scissors, then seal him back up. Crusty mimics oral sex with it, then violates the earlier female victim with it.
Scenes of the three killers in town tormenting a shopkeeper, eating fast food, and wandering around follow, followed by Maggot and Peter watching and masturbating to Crusty torturing two women, sexually abusing and repeatedly vomiting on them while a male corpse rots in the corner of the room. Eventually, the women are killed. Maggot disembowels one, chewing on her spilled innards and having sex with them, while the other is beaten to death by Crusty and Peter, the latter dragging the body away to presumably have sex with it. The three then get drunk, and afterward Maggot is found in the bathroom by his sister, shaving and cutting himself to "look beautiful" for Crusty.
The trio are next shown playing in the snow, attending a concert, meeting up with friends, raping a woman, and going to a piercing shop, where Maggot receives a nose ring, and gets into a fight with Peter over his relationship with Crusty. The group then visit another serial killer, who shows them the contents of his shed; mutilated bodies, dying victims, and a headless and maggot-covered toddler, which Maggot eats a chunk of. Later, while the others are asleep, the new killer borrows their camera, and films himself taunting and slitting the throat of one of his female captives.
When next seen, the trio have attacked a family, killing the father first by hanging him. While Peter tortures the mother, Crusty watches Maggot have sex with the corpse of the young daughter in a bathtub. The three get into a fight, which ends with Maggot slitting his own throat, followed by the film cutting to static. In a post-credits scene, a cat is shown killing and eating a mouse. In the same DVD, there is an altered form called "Maggot's Cut." In this, the whole point-of-view is seen through Maggot's eyes, and it is revealed that he is actually of the opposite gender.Cristie Whiles as Crusty
Fred Vogel as Peter Mountain
Michael Todd Schneider as Maggot
Jerami Cruise as Man Shown Having Sex in Window
Killjoy as Fourth Killer
Midian Crosby as Brunette Vomit Torture Victim
Elmo Painter as Blonde Vomit Torture Victim
Dave Brown as Dead Man in Vomit Torture Sequence
Art Ettinger as Male Friend
Rick Kundrach as Jonesy
Tim Grubjesik as Dead Junkie
Allana Sleeth as Female Friend
Shelby Vogel as Fourth Killer's Victim/Dead Mother
Chris Shaw as Dead Father
Daisy as Daisy
The exploitation film database The Worldwide Celluloid Massacre has Mordum ranked as the fourth most "vile" film viewed by the website, below Salò, or the 120 Days of Sodom Carcinoma and The Angel's Melancholy. The review of the film (which is categorized as "worthless") referred to it as "pointless hardcore depravity".
While traveling to Canada to attend the Rue Morgue Festival of Fear in Toronto, co-director and writer Fred Vogel was arrested, pending charges of transporting obscene materials into Canada, when copies of Mordum and its predecessor were found by customs officials among the merchandise he had intended to bring to the convention. The charges were dropped, after Vogel had spent roughly ten hours in customs prison, and his films were sent to Ottawa for further observation.
Copies of Mordum were confiscated by Australian customs officials in 2004, the reason given for the seizure of the DVDs being that "they offend against the standards of morality, decency and propriety generally accepted by reasonable adults to the extent that they should not be imported".