Four couples gather for a regular brunch which, over the years, has devolved into a gathering fraught with tension and awkwardness. One guest (Glenn) is meeting the others for the first time, on his third date with Tracey, the notoriously picky doctor in the group. As they settle into the afternoon (awaiting an “always late” fifth couple, Jenny and Gordon), they get to know the new member of the group and catch up on old times. When the men excuse themselves to watch football, they discover the TV, Internet, and landline phones are down. When the host, Pete, accuses his wife Emma of not paying the bills, their upcoming divorce is revealed to the guests.
After a neighbor, Hal, appears in a hazardous materials suit with news of dirty bombs exploding in major U.S. cities, including one 12 miles downtown from them, the couples begin to accept that a disaster has occurred. They split up to search the house for emergency supplies and air seal it with duct tape. Throughout the hunt, revelations of affairs between both hosts and two guests, Buck and Lexi, are made, as are rejected sexual advances by the swinger couple toward Glenn who rebuffs them.
Through a shower radio, they hear an automated public advisory that the bombs contained the VX nerve poison. The chemistry teacher, Hedy, in the group understands that because the attacks were chemical, only hours remain before a gruesome death for them all. After going into a trancelike shock, she breaks her silence by asking for Scotch. She later mixes up a batch of “poor man’s ecstasy” from what she raided from a medicine cabinet, has an epiphany and calls off her six-year engagement to Shane. Her spirits lifted, she champions a musical session/”dance party” in the living room, accompanied by Lexi and Buck.
Her now-former fiance is a comic book trader and bases his survival strategy on what he’s learned from zombie films like Night of the Living Dead. After hearing of the bombs, he becomes highly suspicious of outsiders (including the new guy) and suggests others watch for bite marks or odd behavior, and they find weapons (like crowbars and chainsaws). He becomes concerned by the lack of life immediately outside the front window, so he questions the doctor guest about how quickly “mutations” should appear and spread. She explains how genetic mutation really works, with some disdain, but later agrees to not let the late fifth couple into the house when they finally arrive, with the pair visibly sick with something. While he seems more concerned by the woman’s vague and rushed description of the situation outside, her decision to leave them is also partly punishment for always being late and for a past grievance between the two women over a man at a New Year’s party.
Shane decides the best option is to leave the house and drive blindly till he either reaches fellow survivors or runs out of gas, having at least died trying. He asks if anyone’s coming with him, and they all load into his SUV. However, the battery had been drained after leaving the vehicle on while listening to satellite radio, so it doesn’t start.
The group eventually decides to stay home and have their meal as planned, enjoying what time they have. Glenn goes to the cellar to fetch wine, and is discovered by his date adding rat poison, sleeping pills, and muscle relaxants to it. He explains that he’s a firm believer in The Last Judgment, this is likely that and he wants to save his new “non-believer” friends from experiencing the worst of the Great Tribulation. Convinced he’s crazy, she goes upstairs and tells the others, who express their doubt in his craziness and their belief in her tendency to overreact, after the wine is poured, but before they drink. Glenn calmly admits it, and gives his reasons. They’re unconvinced but Hedy agrees their deaths would be easier this way, without the VX symptoms she details.
After some debate, they all agree to drink the poison together on the count of three. After one count, everyone only pretends to drink, including Glenn, who says he figured that might happen. They again ready themselves and finally tip the glasses back in unison. Again, they all fake it. Their fate is left unknown.