Crisis on Earth-X, Part 4

"Crisis on Earth-X, Part 4" is the upcoming eighth episode of the third season of DC's Legends of Tomorrow, and the forty-first episode overall. The episode is the final part of a four-part crossover with the eighth episode of the third season of Supergirl, eighth episode of the sixth season of Arrow and eighth episode of the fourth season of The Flash. It will air on November 28, 2017.

Synopsis
Barry and Iris’s 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, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth's mightiest heroes - Green Arrow, Supergirl, The Flash and White Canary - lead their teams into battle to save the world.