“The Host,” based on Stephenie Meyer’s novel, explores a future where Earth is overtaken by parasitic aliens. Andrew Niccol’s adaptation follows Melanie Stryder, played by Saoirse Ronan, as she battles for control of her body against an alien presence. The film blends romance, action, and dystopian themes, offering a unique take on alien invasion. With a focus on internal conflict and identity, “The Host” provides an intriguing and emotional sci-fi narrative.