"Worlds Finest" -- 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 (Italia Ricci, left), and Livewire (Brit Morgan, right) in exchange for her help in finding a way to return him home, on SUPERGIRL, Monday, March 28 (8:00-9:00 PM, ET/PT) on the CBS Television Network. Photo: Robert Voets/Warner Bros. Entertainment Inc. ÃÂ© 2016 WBEI. All rights reserved. | Episode 1.18 - Worlds Finest | Promotional Episode Photos | Season 1 | Supergirl | Gallery

SpoilerTV Image Archive | Gallery | Supergirl | Season 1 | Promotional Episode Photos | Episode 1.18 - Worlds Finest | "Worlds Finest" -- 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 (Italia Ricci, left), and Livewire (Brit Morgan, right) in exchange for her help in finding a way to return him home, on SUPERGIRL, Monday, March 28 (8:00-9:00 PM, ET/PT) on the CBS Television Network. Photo: Robert Voets/Warner Bros. Entertainment Inc. ÃÂ© 2016 WBEI. All rights reserved.

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