Supergirl 1x18 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.<br>Official website: <br>Official Twitter page: <br>Official Facebook page: <br>Supergirl 1x18 Promo/Preview Worlds Finest<br>Supergirl Season 1 Episode 18 Promo<br>Supergirl 1x18 Promo Worlds Finest (HD)
