Plot: 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.
![Cast and Crew in Supergirl - Season 1 - Episode 18 - Worlds Finest Poster of Cast and Crew in Supergirl - Season 1 - Episode 18 - Worlds Finest](http://es.actoragecheck.com/limage/LzI5S0pLcnAwd3huaXhGWExmTkdUTkNFQkl5Yi5qcGcAACh231.jpg)
Supergirl - Season 1 - Worlds Finest (Episode 18)
Episode Aired On:
Monday, March 28 2016
8 years ago
Monday, March 28 2016
8 years ago