A huge generational colony spacecraft called The Ark has gone off-course. Many of the descendants from the original crew and colonists are unaware that they are aboard a ship.

Fashion model Sarah Cornell, from the front car of a subway, witnesses a man pushing a woman onto the tracks to her death. Hoping to dispel the presumption that the woman committed suicide, Sarah contacts the police. But when they arrive to take her statement, she recognizes one of the detectives as the killer. Can she get anyone to believe her before she becomes his next victim?