Rachel catches the same commuter train every morning. She knows it will wait at the same signal each time, overlooking a row of back gardens.

 She's even started to feel like she knows the people who live in one of the houses. Their life - as she sees it - is perfect. If only Rachel could be that happy.

 And then she sees something shocking, and in one moment everything changes. Now Rachel has a chance to become a part of the lives she's only watched from afar.