Supergirl 1x18 - 4 Sneak Peek Clips (The Flash Crossover)

Supergirl 1x18 “Worlds Finest” Sneak Peeks - The Flash arrives in National City from an alternate universe. He teams up with Supergirl to battle the villains Livewire and Silver Banshee, in exchange for Supergirl’s help finding him a way to return home.