The Girl on the Train” is grounded in the tranquil house-beautiful fetishism of the Hudson Valley suburbs, to the point that you sometimes feel you’re watching “Pottery Barn Catalogue: The Movie.” For a while, though, we seem to be trapped in a spin on “Fatal Attraction” in which the aggrieved feminine stalker is the heroine. How badly does Rachel act? She sneaks into her tastefully exquisite former home, where Tom and Anna now live ( it’s the paradise she was kicked out of) , and coddles their infant in the backyard, pretending it’s the child she couldn’t have. She drinks like a homeless derelict, inviting the stares of passengers on the train. And, in fact, she nearly is homeless: She’s been crashing for two years on a spare bed offered by a friend, and the reason she joins the commuter horde traveling into Manhattan each morning has nothing to do with the PR job she once held. Everything snaps when she oversees the mysterious Megan kissing a stranger, betraying her husband. Just like Rachel was betrayed! Shortly after that, she returns late at night, only now she’s a mess, her hair and clothing caked with blood and mud. On that very night, Megan goes missing. Rachel, of course, has blacked out what happened, but she’s haunted by an image of herself approaching Megan, raising a weapon…