Worlds Finest Supergirl : Season 1 Episode 18
TV-PG The CW 43m
Aired: March 28th, 2016 @ 9:00 PM EST on The CW
Kara gains a new ally when the lightning-fast superhero The Flash suddenly appears from an alternate universe and helps Kara battle Siobhan, aka Silver Banshee, and Livewire in exchange for her help in finding a way to return him home.
