Don't let “based on the novel by Stephenie Meyer,” scare you off. The Twilight author's helpless touch is nowhere near the surprising sci-fi romance The Host. That's likely due to screenwriter and director Andrew Niccol (Gattaca, Lord of War), who tells the tale of a passive alien invasion that replaces people with the pleasantly polite “Souls.” When teenager Melanie's original personality remains behind, she guides her new alien, Wanderer, back to humanity's secret refuge. There begins one of the more complicated love triangles in recent memory, with Melanie trying to convince her previous boyfriend she's not a monster, while Wanderer falls in love with the one boy not trying to kill her. Star Saoirse Ronan deserves special praise, playing both Melanie's sassy internal voiceover as well as Wanderer's wide-eyed alienness. Barely interested in the antagonists threatening Earth, The Host thankfully spends more time contending with weightier issues of identity and what it means to be human.