Emily Blunt stars as lonely, alcoholic divorcee Rachel Watson, who spends a part of every day commuting on a train, looking at the goings-on in a couple of homes that happen to be along the suburban New York route. One of those homes happens to be her former residence, where her ex-husband Tom, who Rachel has yet to get over as evidenced by her persistent drunk dialing and texting to him, is inhabiting with his new wife Anna, and their newborn child. Another home, just a couple of houses down, has another happy couple, Scott and Megan Hipwell, which makes consummate train-wreck (no pun intended) Rachel so envious, she drowns her jealousy toward those living the perfect Stepford-esque life the once had with more bottles of vodka, causing paranoia, blackouts and otherwise erratic behavior. When Rachel spies Megan with another man, then goes missing, she thinks she may have a clue to what may have happened to her, getting involved in ways that make her a potential suspect -- or a potential target. If only she could remember all of the details through her drunken blackouts.