S5, E9: In the kickoff to the epic Crisis on Infinite Earths crossover event, The Monitor (LAMONICA GARRETT) sends Harbinger (guest star AUDREY MARIE ANDERSON) to gather the worldís greatest heroes ñ Supergirl, The Flash (guest star GRANT GUSTIN), Green Arrow (guest star STEPHEN AMELL), Batwoman (guest star RUBY ROSE), White Canary (guest star CAITY LOTZ), The Atom (guest star BRANDON ROUTH) and Superman (recurring guest star TYLER HOECHLIN) ñ in preparation for the impending Crisis. With their worlds in imminent danger, the superheroes suit up for battle while Jíonn and Alex recruit Lena to help them find a way to save the people of Earth-38.