Moments after departing from the Hollywood & Highland Metro Station, commuters on L.A.'s subway system experience a sudden explosion. Most passengers die on impact as the train is violently derailed and sent smashing into the tunnel's walls. In a small pocket deep underground the few survivors soon discover that the danger has just begun. Not only are they trapped between the collapsed tunnel and the twisted remains of the metro, but the passengers also uncover a second bomb that has yet to detonate. As the timer counts down to certain death, the trapped survivors begin to suspect that the first bomb exploded prematurely---and that the terrorist has been trapped among them. It's up to Tori to find the answer to these questions, and she's running out of time. With an unexploded bomb, a missing gun, and a group that's quickly turning on one another, the rescue crews might not arrive in time to save the survivors from themselves.