The Host (2013)

Another adaptation from Stephenie Meyer. But before you turn your head in disgust, you should know The Host has no vampires and half naked werewolves, only aliens. In a future world where aliens (or souls, as they are called in the film) have taken over humans bodies, Saoirse Ronan plays not one, but two characters. The soul Wanderer (Wanda for short) has been inserted into the human body of Melanie Stryder. In an attempt to discover the whereabouts of a small pocket of the human resistance, Wanda's job is to provide this information to The Seeker (Diane Kruger).

Max Irons and Saoirse Ronan in a flashback scene. Source: Cineplex