The epic four-way crossover with "Arrow", "Supergirl", "The Flash" and DC's Legends of Tomorrow" continues.
Barry (Grant Gustin) and Iris's (Candice Patton) wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony.
All of the superheroes band together with help from their super friends like Citizen Cold (guest star Wentworth Miller), The Ray (guest star Russell Tovey), Felicity Smoak (guest star Emily Bett Rickards), Iris West and Alex Danvers (guest star Chyler Leigh) to take on their most formidable villains yet. Earth's mightiest heroes -- Green Arrow (guest star Stephen Amell), Supergirl (guest star Melissa Benoist), The Flash (Grant Gustin) and White Canary (guest star Caity Lotz) – lead their teams into battle to save the world.
