After numerous attempts in many different time periods, the team has successfully captured Vandal Savage. However, Savage tells Kendra that he can reunite her with Carter so she struggles with whether she should kill him. Rip decides they will deliver Savage to the Time Masters which doesn’t sit well with Snart and Rory. The duo decides it may be time to jump ship and return to their old life. Meanwhile, Savage taunts Ray about his place in Kendra’s life.

After the numerous sacrifices the team has made since the beginning of this ride, Rip decides that it’s time they each decide their own destiny and returns them to Central City a few months after they first left. Returned to their normal lives, each team member must individually decide if they are willing to sacrifice everything in order to save the world. Meanwhile, Sara visits with her father who delivers some heartbreaking news about her sister.

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.

The crossover starts on Supergirl S03E08 Crisis on Earth-X (I), Arrow S06E08 Crisis on Earth-X (II) and The Flash S04E08 Crisis on Earth-X (III).