By chance, musician Harry Washello meets waitress Julie Peters at the La Brea Tar Pits museum. After a day of romance that includes taking Julie’s grandfather, Ivan, to listen to Harry play an outdoor jazz concert, they arrive at the La Brea apartment complex to find Lucy, Julie’s grandmother, waiting. Upon seeing Ivan, Lucy walks away. Julie explains that they have not talked to each other after an argument fifteen years earlier. Since Harry is leaving the next day, he and Julie make plans to meet after her shift as a waitress at Johnnie’s Diner. They share a kiss, and Julie promises sex on the third date. Harry goes to his hotel, lights a cigarette, takes one puff and throws it off his balcony, where a crow retrieves it and takes it to her nest on the hotel’s high voltage lines. The nest bursts into flames, knocking out the hotel’s electrical power. Unaware of this development, Harry takes a nap and oversleeps. Julie waits for an hour before deciding Harry is a no-show. When Harry wakes up and realizes he is late, he rushes to Johnnie’s and begs a waitress to give him Julie’s telephone number. As he enters a telephone booth, the telephone rings. He answers it to hear a panicking man screaming that the U.S. is launching nuclear missiles in one hour. The man identifies himself as Chip and explains that he is calling form a North Dakota missile silo, trying to reach his father. However, he got the wrong area code. Harry hears gunshots and Chip screams. Another voice comes on the line and orders Harry to forget what he just heard, then hangs up. Stunned, Harry walks into the restaurant’s glass door and gets a nosebleed. He looks around the diner and sees two street maintenance workers, Harlan and Mike, sexually harassing Landa, a stock broker, while a stewardess practices hand gestures for an airline’s safety speech. Harry screams for everyone to shut up, and repeats what Chip said about nuclear war. No one believes him until Landa telephones a governmental official and learns that the military is on high alert. Pandemonium breaks out as patrons argue over what to do. Frank, the short-order cook, pulls a revolver and fires a shot into the air, demanding that Harry admit he is joking. When Harry sticks to his story, Frank runs into the back room to gather supplies. Landa has Harry repeat verbatim Chip’s telephone call and declares the numbers Harry heard are launch codes. After making a few more calls, Landa learns that the four highest executives of the Rand Corporation are flying to the southern hemisphere. Only Harlan disbelieves war is imminent. He curses the patrons as they leap into Frank’s catering truck to rush to the airport. Landa explains there is a valley in Antarctica that will shelter them from a nuclear blast. The busboy steals Harry’s car, so Harry leaps into the catering truck and orders Frank to drive to Julie’s. Frank refuses to comply. Landa informs Harry she has just arranged a helicopter to collect food, clothing and weapons at the nearby Manhattan Building. If he can retrieve Julie and be there in fifty minutes, the pilot will take them to the airport. Refusing to stop, Frank slows down so Harry can leap out. Harry flags down a car and uses Frank’s gun to force Wilson, the driver, to take him to Julie’s. They stop for gas on the way. As Harry calls Julie's grandfather, Ivan, to explain what is happening, a station attendant appears with a shotgun and accuses Wilson of stealing gas. A police cruiser arrives and orders the attendant to drop his gun. Wilson, who has stolen electronics in his trunk, sprays the police with gasoline. One of the officers discharges her firearm, causing the sparks that set her and her partner on fire. Harry and Wilson leap into the squad car as the flames reach the pumps and blow up the station. At Julie’s apartment complex, Harry tells Wilson about the helicopter and asks him to wait four minutes. When no one answers the door, Harry kicks it down and is almost shot by Lucy. Quickly explaining the situation, Harry rushes in to find Julie passed out from a Valium. Hearing honking, he looks out the window and sees Wilson drive off in the police car. Carrying Julie to the lobby, Harry and Lucy find Ivan. The old couple bursts into tears and rush to get their car while Harry takes Julie outside. He places her into a shopping cart and starts running toward the Manhattan Building. Julie wakes up, but in her groggy state, thinks she and Harry are on their way to ride in a hot air balloon. Ivan and Lucy appear outside the meeting point, but tell Harry they want to die together and drive off to Canter’s Delicatessen. Still addled by the Valium, Julie wants to go with the elderly couple, but Harry rushes into the building and takes the elevator to the roof. He discovers the helicopter and the supplies, but Landa’s assistant, Gerstead, informs Harry the pilot has yet to arrive. Gerstead accuses Landa of perpetrating an elaborate prank. Harry grabs a wad of cash from Gerstead. Leaving Julie with the helicopter, he goes to a gym in search of a helicopter pilot. No one can hear him over the music, so Harry shoots out the speakers. A powerlifter asks what the emergency is. Harry claims a toxic fire has erupted, sending poisonous gases their way, and the lifter admits he can fly a helicopter. As they leave the gym, Harry hears Julie shouting for a pilot. Harry tells the powerlifter to go to the heliport and runs after Julie. Just as he reaches her, a police cruiser speeds by, loses control and smashes into a department store. Wilson steps out of the car, carrying his dead sister, and collapses. Realizing he is too wounded to go on, Wilson begs Harry to shoot him, but dies before Harry can pull the trigger. Police surround the building, and Harry realizes an hour has passed with no bombs falling. He runs to a telephone booth and calls the phone number Chip was trying to reach. The voice on the other end confirms he is Chip’s father. As people flood the streets and loot shops, Harry hands his gun to Julie, and tells her to get up to the roof. Air raid sirens blare, and a man panics and starts shooting at Harry, who crawls into a storm drain to get away. He crawls through the sewers to reach the Manhattan Building, and finds Julie waiting in the lobby. Upon reaching the roof, they find a drugged Gerstead but no helicopter. As a missile flies overhead, they hear the helicopter approach. It is the powerlifter returning for them. Gerstead still refuses to board. The helicopter lifts off just as a missile explodes in the San Fernando Valley. The helicopter crashes into the tar pit, killing the pilot. While the helicopter sinks, Harry and Julie profess their love. Another missile explodes, vaporizing them.