Supergirl Season 4 Episode 9
Season 4
Episode: 9
Air Date: 2018-12-11
Supergirl, The Flash, Green Arrow and Superman engage in the battle of their lives. The crossover starts on The Flash S05E09 Elseworlds (I) and Arrow S07E09 Elseworlds (II).
Episode Title: Elseworlds (III)