“The Girl on the Train” is a psychological thriller novel written by Paula Hawkins, published in 2015. The story revolves around Rachel Watson, an alcoholic woman who takes the same commuter train every day. During her journey, she observes a seemingly perfect couple from the train window and becomes drawn into their lives. However, when the woman from this couple goes missing, Rachel becomes entangled in the investigation and discovers dark truths about herself and those around her.