Supergirl’s struggle against Leviathan reaches a boiling point as she faces off against Rama Khan. As Lena and Hope work to launch Project Non Nocere, Hope proves to be an invaluable asset to Lena.

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. 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.

Pariah enlists Black Lightning to help stop the Anti-Monitor after Flash-90 Shares what he learned from his battle in Elseworlds. With Black Lightning’s help, Barry Cisco and Killer Frost come up with a plan that could save them. Iris has a heart-to-heart with Ryan Choi. Oliver and Diggle return to an old familiar stomping ground.