The Game of Thrones actress portrays Fay, a teenager who has the sneaking suspicion that she is being followed by a dark force.
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Fay's school classes, photography trips and rendezvous with her boyfriend (Gregg Sulkin) all seem to be observed by someone who looks exactly like her.
Rhys Ifans, Jonathan Rhys Meyers and Claire Forlani all have supporting roles in director Isabel Coixet's thriller.
Coixet is an acclaimed Spanish filmmaker who has previously found international success with Elegy and The Secret Life of Words.
Another Me is expected to open later this year.