The Monitor sends Harbinger to gather the worlds' greatest heroes - Supergirl, The Flash, Green Arrow, Batwoman, White Canary, The Atom and Superman - in preparation for the impending Crisis. With their worlds in imminent danger, the superheroes suit up for battle while J'onn and Alex recruit Lena to help them find a way to save the people of Earth-38. The group uses Ray's invention to track new recruits to help save the universe. The Monitor sends Iris, Clark and Lois in search of a mysterious Kryptonian, while Kate and Kara head out to find Bruce Wayne. In addition, Mia challenges Sara, Rory discovers a hidden talent, and Lex Luthor returns.