The Girl On the Train - Summarized for Busy People: A Novel: Based on the Book by Paula Hawkins

Each day is as mundane as the last. Rachel Watson travels to and from London by train, and on the way, she passes the fine suburban houses owned by the people living the life she once dreamed of living.

Aboard the morning train, Rachel sees "Jason" and "Jess", her perfect couple, eating breakfast together on the deck of their beautiful home. One day, Rachel witnesses something that would linger in her mind. The sight is fleeting, but a few moments are more than enough.

When an investigation is opened in search of the woman who went missing, Rachel steps forward to give her testimony. At the state she is in, the police deem her to be unreliable as a witness. Rachel knows much more than what her mind allows her to remember. She crosses a line she cannot turn back from when she finds herself too involved in the case of the missing woman. Rachel's efforts to unravel the mystery lead her to conclude that everything she has come to know is a lie.