As you know from Supergirl, Barry and Sisco went to get Supergirl from her Earth to come and help them on Earth-1 against an alien invasion. The Dominators came to Earth-1 and looked to destroy the world before they became a future threat. With the numbers Barry knew he needed more help and with Sisco’s vibe assistance was able to get a successful portal to Kara’s world again.
Barry also went to Star City to recruit Green Arrow to help him with the attack. They also made contact with the Legends of Tomorrow to come and join them. You had the Flash, Supergirl, Arrow, Spartan, Speedy, White Canary, Firestorm, Atom, Heatwave, and Citizen Steel. The group decided they had to get some practice together and the best way to get prepared to fight aliens is to spar against an alien. With Supergirl being the most overpowered of the group they practiced against her and got their asses handed to them over and over again.
Professor Stein and Jackson pulled Barry aside to talk to him about what they found on the Waverunner. It was a recording of Barry 50 years in the future, telling Rip Hunter that he messed up, the future is in danger and he can’t be trusted. Stein and Jackson tell Barry he needs to come clean to the team. Sisco later finds the tape recording and wants to tell the team, Barry does, reluctantly at first, inform the team of what is on the recording. How he messed up by going back in time to save his family, thus creating Flashpoint that altered the lives of some people in this universe. Sisco’s brother was lost, John Diggle had a daughter in the other timeline and other changes. The team decides minus Green Arrow (who is the only one who insists that Barry can be trusted) go on the mission to save the President who was captured by the Dominators. The ‘geeks’ team is able to pinpoint an aberration of where they believe the President is, the team tracks him down to a warehouse. The team, stupidly I might add, does not really take precaution or survey the situation, go in blindly to get the President to find out it’s a trap. The Dominators incinerate the President and put the rest of the team in mind control.
All of the team is compromised and returns to base where Green Arrow and Flash try to fight back against them. Being outnumbered and outgunned the pair is under heavy fire, Wally West who is inside and has powers his family doesn’t want him to use rushes out to save them from the attack but is hurt badly in the process. Green Arrow is cornered and needs to protect Wally and retreats into a bunker who is being chased by White Canary, Guardian and Speedy. He is able to use his arrows to create some separation but is in a precarious situation when he runs out of arrows.
While this is happening, Barry is able to lure Supergirl back to the warehouse where they were mind controlled. Their is a glowing orb that is the power source for the mind control and Flash knows that Supergirl is invincible and the best course of action is to have her destroy the orb. So Flash challenges her to a race and is running in a pattern that will cause the structure to destruct if need be. After enough speed is created Flash runs past the orb and Supergirl flies through the orb destroying it and effectively destroying the mind control over the heroes. It happens at the right time for Green Arrow who was dead to rights.
Flash and Supergirl return to the rest of the team so they can try to figure out the next course of action. While walking in Oliver Queen, Sarah Lance, John Diggle, Thea Queen and Ray Palmer are abducted into a Dominators space ship.
What is the fate of our heroes? Find out in part 3 of the Crossover event on Arrow.