Rachel takes the same commuter train every morning, flashing past a stretch of cozy suburban homes, and stopping at the signal that allows her to daily watch the same couple breakfasting on their deck. Their life, as she sees it, is perfect ... until she sees something shocking. It's only a minute until the train moves on, but now everything is changed. Rachel goes to the police, and becomes inextricably entwined in the lives of everyone involved....

A businessman is caught up in a criminal conspiracy during his daily commute home.

"It all happens so quickly. One day you're living the dream, commuting to work by ferry with your charismatic neighbor Kit in the seat beside you. The next, Kit hasn't turned up for the boat and his wife, Melia, has reported him missing. When you get off at your stop, the police are waiting. Another passenger saw you and Kit arguing on the boat home the night before and the police say that you had a reason to want him dead. You protest. You and Kit...

Rachel is unemployed and devastated by a recent divorce. She fills her time with drinking, riding the commuter train, and fantasizing about a seemingly perfect couple the train passes by every day. Then one morning, Rachel sees something shocking that unravels her and entangles her in an unfolding mystery.