Description
The Earth is passing through the tail of a comet, an event which has not occurred in 65 million years and coincided 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 Tempest video game, on which all the other scores are hers. She stays after the theater closes to assist her boyfriend Larry, the theatre’s projectionist to sneak back in so he can loan out a film reel for illegal duplication for his own profit. He offers to pay for her assistance from what he expects to earn when the other party returns the film reel in the morning. Reggie and Larry spend the night in the steel-lined projection booth and have sex.
Meanwhile, Reggie's 16-year-old sister Samantha "Sam" argues with their stepmother Doris, who Sam implies is cheating on her father. It is revealed during the argument that Sam and Reggie’s father is away on active military duty. Doris, upset by Sam’s accusation, slaps her in the face. Sam retaliates and slaps Doris back. Doris then punches Sam in the face sending her flying over the couch and onto the floor. Sam ultimately spends the night in a steel backyard shed.
The next morning, a gloomy reddish haze covers the sky and there are no signs of life but piles of red dust and heaps of clothing everywhere. Unaware that anything has occurred, Larry goes outside and is killed by a zombie wielding a pipe wrench. After playing the video game to replace DMK’s initials with her own, Reggie goes looking for Larry outside, mistaking the red overcast sky as bad smog. She quickly encounters the zombie, but escapes on Larry’s motorcycle. She heads home to find her sister and they surmise that because they both spent the night in steel containers, they were saved from the comet's effects.
The sisters race to the local radio station after they hear a disc jockey on air, only to find it was a pre-recorded show. 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 check if any of his family survived, but promises to return as soon as possible.
Reggie and Sam then go shopping for guns and clothing 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 she diagnosed as having been exposed to the comet due to her developing rash and to wait for Hector to return. After she fakes euthanizing Sam by injecting her with only a sedative, 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. Sam and Hector set out to rescue Reggie.
Back at the base it is revealed that the researchers had suspected and prepared for the comet's effects, but inadvertently left the ventilation system open and the fans running during the comet's passage. This allowed the deadly dust to permeate their base. 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 young boy and a girl before they are processed, then unplugs the other victims from their life support machines. Sam and Hector arrive and rescue the trio and blow up the scientists.
Eventually, rain washes away the red dust, leaving the sky clear. After Reggie pairs up with Hector, and takes parental roles with the kids, Sam feels left out. Frustrated, she ignores Reggie's warning about crossing a deserted downtown street against the still-operating signal light, claiming there isn't anyone else left Sam is almost run over by a sports car driven by Danny Mason Keener, a survivor 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.
