The Earth is passing through the tail of a comet, an event which has not occurred in 65 million years and coincidentally with the extinction event that wiped out the dinosaurs. On the night of the comet's passage, which takes place eleven days before Christmas, large crowds gather outside to watch and celebrate.
18-year-old Regina "Reggie" Belmont works at a movie theater in southern California. She is annoyed to find the initials DMK have the sixth highest score on the theater's arcade game on which all the other scores are hers. She stays after the theater closes to play until DMK's score is removed and to have sex with her boyfriend Larry, the theater projectionist, in the steel-lined projection booth. Meanwhile, Reggie's 16-year-old sister Samantha "Sam" argues with their stepmother Doris, who punches her in the face. Sam then spends the night in a steel backyard shed.
The next morning, a reddish haze covers everything, and there are no signs of life, only piles of red dust and heaps of clothing. Unaware that anything strange has happened, Larry goes outside and is killed by a zombie wielding a pipe wrench. When Reggie goes looking for Larry, she encounters the zombie, but escapes. She heads home to find her sister. Because both Reggie and Sam spent the night shielded from cosmic effects by steel, they were saved from the comet's effects.
After figuring out what has happened, they hear a disc jockey and race to the radio station, only to find it was just a recording. They come across another survivor there, Hector Gomez, who spent the night in the back of his steel truck. When Sam talks into the microphone, she is heard by researchers in an underground installation out in the desert. As they listen to Reggie, Sam and Hector debate what to do, the scientists note that the zombies, though less exposed to the comet, will eventually disintegrate into dust themselves. Hector leaves to see if any of his family survived, but promises to come back. Reggie and Sam then go shopping at a mall. After a firefight with some zombie stock boys, the girls are taken prisoner, but are saved by a rescue team sent by the scientists.
Reggie is taken back to their base. Audrey White, a disillusioned scientist, offers to dispose of Sam, who was diagnosed as having been exposed, and to wait for Hector. After she fakes euthanizing Sam by injecting her with a sedative that only put her to sleep, she kills the other remaining scientist. When Hector returns after an encounter with a zombie child, Audrey briefs him on the situation and then gives herself a lethal injection. He and Sam set out to rescue Reggie. The researchers had suspected and prepared for the comet's effects, but inadvertently left their ventilation system open and the fans running during the comet's passage, allowing the deadly dust to permeate their base. Meanwhile, Reggie has become suspicious, escapes, and discovers that the dying scientists have hunted down and rendered healthy survivors brain dead. They harvest their untainted blood to keep the disease at bay while they search desperately for a cure. Reggie saves a boy and a girl before they are processed, then unplugs the other victims from their life support machines. Hector and Sam get the trio out of the base.
Eventually, rain washes away the red dust, leaving the world in a pristine condition. After Reggie pairs up with Hector, Sam feels left out, as the others are kids. When she ignores Reggie's warning and crosses a deserted street against the still-operating signal light, she is almost run over by a sports car driven by Danny Mason Keener, a teenager about her own age. After apologizing, he invites her to go for a ride. As they drive off, the car is shown sporting the initials "DMK" on the vanity plate.
When writing the script, director Thom Eberhardt wanted to merge the idea of strong female protagonists with his love of post-apocalyptic films set in empty cities. For the women, he was inspired by Ginger Rogers. Further inspiration came from real-life teenage girls whom he met while filming PBS specials. Without telling the girls details about the script's premise, he asked them to describe how they would react to an apocalyptic event. The girls saw the scenario as an exciting adventure and only saw a downside to the experience when Eberhardt brought up the subject of dating. Using their answers, Eberhardt wrote the script to be lighthearted and adventuresome. Eberhardt initially had trouble convincing the studio to let him direct it, but they relented when he held out, as Atlantic Releasing Corporation was looking to immediately invest $700,000. Atlantic also wanted to capitalize on the success of their 1983 hit Valley Girl and the popularity of quirky drive-in films like Repo Man. The producers, Andrew Lane and Wayne Crawford, clashed with Eberhardt during filming; Eberhardt would later say that they did not understand the film and resented being assigned to such a low-budget B movie. Early in the production, they attempted to have him replaced. Regardless, Eberhardt praised their producing skill and said the film could not have been made without their help. Heather Langenkamp auditioned for the role of Samantha "Sam" Belmont and was the number one choice on the casting list but the part ultimately went to Kelli Maroney.
Atlantic released Night of the Comet in the US on November 16, 1984, earning $3,580,578 in its opening weekend, coming in at third place. It stayed in theaters for six weeks and grossed $14,418,922 total in the US. The film is also noted as one of the first mainstream films to carry the MPAA PG-13 rating.
Night of the Comet was released on VHS cassette and CED Videodisc on August 30, 1985, and distributed by CBS/FOX Video. A second U.S. VHS printing, distributed by Goodtimes Video, was released on August 30, 1990. MGM released the film on DVD in the US on March 6, 2007. The film was released in a Collector's Edition on Blu-ray by Shout! Factory on November 19, 2013. Sherilyn Connelly of The Village Voice criticized the marketing of the Blu-ray, saying that it dumbs down the film and portrays the independent women as helpless stereotypes.
A soundtrack for the film was released on vinyl LP record and audio cassette from Macola Records, shortly after the film's release. The soundtrack's "Learn to Love Again", a love duet performed by Amy Holland and Chris Farren, played in the final scene in the film and in the closing credits. Other songs include "The Whole World is Celebratin'" (also performed by Chris Farren), "Lady in Love" and "Unbelievable" by Revolver, "Strong Heart" by John Townsend, "Trouble" by Skip Adams, "Living on the Edge" by Jocko Marcellino, "Virgin in Love" by Thom Pace, and "Hard Act to Follow" by Diana DeWitt.
Rotten Tomatoes, a review aggregator,gave the film an 83% score based on 29 critics' reviews; the average rating is 6.4/10. Variety wrote that Eberhardt "creates a visually arresting B-picture in the neon-primary colors of the cult hit Liquid Sky as well as pointing similarities with Five, The Day of the Triffids, The Omega Man, Dawn of the Dead and Last Woman on Earth. They described the film as "a successful pastiche of numerous science fiction films, executed with an entertaining, tongue-in-cheek flair that compensates for its absence in originality." Vincent Canby of The New York Times called it "a good-natured, end-of-the-world B-movie" whose "humor augments rather than upstages the mechanics of the melodrama". Author Neil Gaiman wrote in 1985 that the film was "one of the most amusing, witty, imaginative, and thought-provoking films I've seen that was made with no budget and is also cheap exploitation."
It has since become a cult film. Keith Phipps of The Dissolve wrote that the film's cult following comes from how matter-of-factly it treats its weird premise. The film was voted number 10 in Bloody Disgusting's Top 10 Doomsday Horror Films in 2009. Maroney's character was an influence on Joss Whedon when he created Buffy Summers of Buffy the Vampire Slayer.