The official plot synopsis for Grant Gustin's upcoming cross-networking guest appearance as The Flash on fellow DC Comics-based series "Supergirl" has been revealed. The anticipated March 28 episode, "Worlds Finest," will, as previously reported, feature a villain team-up between Silver Banshee (played by Italia Ricci and Livewire (Brit Morgan) -- plus, the synopsis confirms speculation that The Flash and Supergirl (Melissa Benoist) do indeed exist in different fictional worlds, as the speedster "suddenly appears from an alternate universe."
Based on the guest cast listed for the episode, Gustin looks to be the only performer from The CW's hit slated for "Supergirl." Additionally, CBS has released a new piece of promo art from the episode, an homage of 1967's "Superman" #199 cover by Carmine Infantino and Murphy Anderson, depicting "Superman's Race with the Flash!" Whether or not Supergirl and The Flash race on March 28 remains to be seen, but here's hoping.
“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 28 (8:00-9:00 PM) on the CBS Television Network. Grant Gustin crosses over as The Flash.
The Flash's guest appearance is the culmination of nearly a year of fan speculation, starting with a Variety cover from last May where Gustin and Benoist both appeared in costume, months before the "Supergirl" series premiere. Beyond both shows being based on famous DC superheroes, they share two executive producers in common, Greg Berlanti and Andrew Kreisberg.
"Supergirl" airs Mondays at 8 p.m. on CBS.