Well that was a thrilling ride. The marketing team is doing a phenomenal job for this movie and I just had to read the book prior to seeing the movie. 
 "There's something comforting about the sight of strangers safe at home." 
 Have you ever sat in a resteraunt people watching? I used to do this thing when I was younger where we'd make up stories for the lives of people around us. That's exactly what Rachel would do everyday on the train. Except there's a particular couple - Jess and Jason (view spoiler)[Megan and Scott (hide spoiler)] - whose lives she becomes too entrapped with. When she witnesses something that she can't forget and runs to tell the police she finds herself involved in a mystery somehow tangled within her own life. 
 "The holes in your life are permanent. You have to grow around them, like tree roots around concrete; you mould yourself through the gaps." 
 We have three POV - Megan, Anna, and Rachel - all leading up to the same moment and climaxing event.