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.

Brit Morgan, Chris Vance, Christopher Showerman, Grant Gustin, Harriet Sansom Harris, Italia Ricci, Jenna Dewan, Sarah Robson