We learn from the opening sequence that aliens have colonised Earth. Palm-sized organisms implant themselves into humans via the neck and take full control of their host. The global host population are docile, compliant. They also have sparkly ice-blue eyes, are conveniently trustworthy and like to drive shiny silver cars and helicopters.
Occasionally a human will resist their body snatcher, which is what happens when Melanie Stryder pits her strong will against Wanderer. Wanderer will speak out loud whereas Melanie will make snide remarks and plead her bodily neighbour inside her head not to divulge information that will threaten the lives of her friends and family who are secluded in the desert.
An overzealous seeker, a host concerned with hunting rebels, pries enough details during an interrogation to track Melanie/Wanderer when they run from the city to the sand. And so we are treated to a protagonist struggling with a split personality disorder and a long-winded plot punctuated by lovey-dovey flashbacks and a seemingly ridiculous love quadrangle that includes Wanderer, Melanie, Melanie's old flame and another random dude.
Ultimately The Host has some interesting science fiction ideas wrapped in a young adult drama for swooning girls and boys. There seem to be missed opportunities, however, to explore themes of identity and love in greater detail because there are recurring questions in the dialogue that make the whole ordeal monotonous. Everyone keeps wondering if Melanie is still alive? And they keep asking over and over and over.
Despite the philosophical repetitiveness, this is a story that reinforces the power of love and should elicit smiles or smirks from the audience.