Information for The Girl on the Train at Southend Palace Theatre, Westcliff-on-Sea (Play). Rachel Watson longs for a different life. Her only escape is the perfect couple she watches through the train window every day, happy and in love. Or so it appears. When Rachel learns that the woman she's been secretly watching has suddenly disappeared, she finds herself as a witness and even a suspect in a thrilling mystery in which she will face bigger revelations than she could ever have anticipated.