Here is the plot for the film.
One soul, the Wanderer, is fused with a captured human named Melanie Stryder, in an attempt to locate the last pocket of surviving humans on Earth.
“The Host” will land in theaters on March 29th, 2013, and stars Saoirse Ronan, Diane Kruger, Jake Abel, William Hurt, Frances Fisher, Max Irons, Chandler Canterbury, and Boyd Holbrook. Andrew Niccol wrote the screenplay, which is based on the novel by Stephanie Meyer. Andrew Niccol directs.
Sources: filmequals.com, IMDb