Commuter Rachel Watson (Emily Blunt) catches daily glimpses of a seemingly
perfect cpuple, Scott and Megan, from the window of her train. One day, Watson witnesses
something shocking unfold in the backyard of the strangers' home. Rachel tells the authorities
what she thinks she saw after learning that Megan is now missing and feared dead. Unable to trust
her own memory, the troubled women begins her own investigation, While police suspect that Rachel
may have crossed a dangerous line.