Married man Charles Schine (Clive Owen) meets Lucinda Harris (Jennifer Aniston), a high powered businesswoman, on a commuter train one morning. An innocent conversation leads to an evening drink. Before either one can stop it, their aroused passions lead to a sizzling one-night stand. Suddenly a stranger explodes into their world, threatening to expose their secret, and lures them into a terrifying game with more surprises than they saw coming.