Being trapped in the subway all alone with someone/something sinister is one of my irrational yet very real (for me) fears. Having taken the subway super late at night when I'm basically one of the only people there. It's very creepy and sometimes the people out there late at night can seem sinister. Love that this film encapsulates and brings to the forefront this fear so effectively for the first half. Second half is a little less intense, once you figure out more details about the "creep." Still a really solid horror movie though, and super underrated.