Ř7, D9: With Oliver and Barry (guest star GRANT GUSTIN) still stuck in each other’s bodies, the two get a lead on John Deegan (guest star JEREMY DAVIES) and head to Gotham City with Supergirl (guest star MELISSA BENOIST) to figure out why their reality has changed. While there, they meet the mysterious Kate Kane (guest star RUBY ROSE) who provides them with information that leads the group to Arkham Asylum.