Earth’s Mightiest Heroes return for their biggest adventure yet in ‘Avengers: Infinity War.’ Iron Man, Captain America, Black Widow, Hulk, Thor, Vision, and the rest of the Avengers team with the Guardians of the Galaxy (and Doctor Strange) to finally take on Thanos, the alien madman intent on collecting the Infinity Stones and conquering the universe. The film was originally announced as a two-part adventure; the fourth ‘Avengers’ is now considered a separate story (with an as-yet unannounced title).