Season 1, Episode 01 – “ Crisis Aftermath I ”

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.