Rachel sees the same couple breakfasting on their deck each morning as she passes by in her commuter train. She thinks their life looks perfect until, one day, she sees something shocking. The train moves on immediately, but she can't keep it to herself and informs the police. Has she done more harm than good?

"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...