Supergirl Season 1 Episode 18
Overview
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.
Director: Nick Gomez
Guest Star: Brit Morgan, Chris Vance, Christopher Showerman, Dan Warner, Dawn Greenidge, Grant Gustin, Harriet Sansom Harris, Italia Ricci, Jay Jackson, Jenna Dewan, Sarah Robson