'The Host'

At the heart of this sci-fi thriller is a long, probing look at the relationship between a girl and ... herself. "The Host" combines real romance with a philosophical approach to the familiar premise of Earth being invaded by aliens. Most of the time, it works. Other times, the hormonal confusion and identity-searching gets to be a bit much.

Based on the novel by Stephanie Meyers (who also authored the smash-hit "Twilight" series), "The Host" wastes no time in telling us the bad news: The human race has been taken over by a race of alien Wanderers — souls that inhabit human bodies and erase the original memories and identities of their hosts. The good news is these Wanderers are smart, sensitive and they love it here. They even stop global warming and deal with pollution.

Teenage protagonist Melanie (Saoirse Ronan) retains her memory even as her body is taken over. That's because the parasitic Wanderer has fallen in love with her. Thus begins an intriguing relationship between Melanie and an inner alien voice that's always advising and warning her. Actually, it's not unlike the relationship one has with an iPhone.