Rachel takes the same commuter train every morning. Every day she rattles down the track, flashes past a stretch of cozy suburban homes, and stops at the signal that allows her to daily watch the same couple breakfasting on their deck. Shes even started to feel like she knows them. Jess and Jason, she calls them. Their lifeas she sees itis perfect. Not unlike the life she recently lost.

And then she sees something shocking. Its only a minute until the train moves on, but its enough. Now everythings changed. Unable to keep it to herself, Rachel offers what she knows to the police, and becomes inextricably entwined in what happens next, as well as in the lives of everyone involved. Has she done more harm than good?