Emily Blunt plays the alcoholic Rachel Watson in “The Girl on the Train,” an adaptation of Paula Hawkins’ best-selling novel of 2015. The film’s real star, though, is Allison Janney as the levelheaded Detective Riley, who is investigating the case of a missing woman. Rachel doesn’t know the woman at all, but she keeps coming to Riley with important new clues she just remembered. Riley’s dry response: “That’s pretty coincidental, isn’t it?”

Thank God for Riley, who says exactly what we’re thinking. “The Girl on the Train” is a preposterous murder-mystery that relies on false flashbacks, misinformation and wild contrivances to hold our interest. When that fails, director Tate Taylor (“The Help”) throws in some soft-core sex to distract us. While the book was touted as the next “Gone Girl,” this inevitable movie — rights were sold even before publication — feels more like a cheesy “erotic thriller” from the 1990s.

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The book took place in London, but the movie is set in the New York suburb of Ardsley-on-Hudson, one of those Peyton Places where misery lurks behind the manicured greenery. Rachel, jobless and depressed (but still British, for some reason), boards the Metro-North every day and broods over her ex-husband, Tom (Justin Theroux), who is now married to Anna (Rebecca Ferguson). Out her window, Rachel also fixates on the abode of hunky Scott (Luke Evans) and his superhot wife, Megan (Haley Bennett). Got all that? Anyway, when Megan goes missing, Rachel inserts herself into the case.

This involves a great deal of lying to people, stumbling around drunk and sifting through murky memories. Hawkins’ adroit writing helped cover up all the baiting-and-switching, but on the big screen there’s nowhere to hide. Our exasperation grows by the minute. We expect characters to lie to us, but not the movie itself.

In the end, “The Girl on the Train” presents us with a silly, shallow story about three despicable women: an inebriated doormat, a spineless trophy wife and a manipulative sexpot. When the villain is finally revealed, twirling his mustache and going bwah-ha-ha, you’ll almost hope he gets away with it.