The Girl on the Train

Rachel Watson is a simple woman, who becomes an alcoholic after the divorce with her husband Tom. The latter has married a girl named Ann and they have born an amazing daughter. Rachel cannon live with it and has started to drink and disturb Tom's new family. Every day she travels on the train near her old house and pay attention to neighbor - Scott and Megan. They are happy couple and their relationships seem to be an ideal.
One day Megan mysteriously disappeared and only the girl on the train is the only witness of her missing. What was happened and what else Rachel may remember?