In the late nineties, the city of Los Angeles completed the most ambitious underground railway project in history. An engineering feat made all the more impressive given the fact that L.A. is one of the world's earthquake hot spots. The Metro Red Line train number 7 is unusually busy for a Saturday night. As the train passes between Universal and Hollywood stations, a massive earthquake strikes. The powerful jolt sends the train crashing into the collapsed tunnel. When the authorities refuse to send in a rescue team, the survivors face a battle for their lives or the prospect of a deep concrete grave.