Supergirl 1×18 Sneak Peek #5 “Worlds Finest”

Supergirl 1×18 “Worlds Finest” – Kara gains a new ally when the lightning-fast superhero The Flash (Grant Gustin) 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, on SUPERGIRL, Monday, March 28th on CBS. Grant Gustin crosses over as The Flash.