Eobard is born 136 years from now. He hated future Barry. Future Barry followed Eobard back in time and saved himself and oh did that make Eobard mad. He stabbed his mother in the heart in a moment of passion to end the man he hated, never realizing he'd have to create the very man he hated in order to return home.
Now, if Barry gives him what he wants, he will give Barry what he wants. Barry wants to kill him, but Harrison admits he looks on Barry with pride and love. He's giving Barry a chance to undo all the evil he's done. Doesn't he want that chance?
Dr. Stein talks with the group about the ramifications of changing one day, the compounded decisions that would be changed and that there is no real way of knowing what his life, or any of their lives would be. Joe doesn't think he has a choice. He has to do it. The choice to grow up with both parents is worth the risk.
Barry goes to see his father at Iron Heights. Henry is surprised that Joe thinks he should do it and disagrees. He launches into one of the most incredible speeches a father would ever tell his son about being proud.
Ronnie tells Caitlin he's home for good. He's only a whole man when he's with her. He wants to marry her.
Iris finds Barry on the roof where she used to meet the streak. She wonders if he's going to do it. Barry thinks growing up together made it hard for him to admit how he felt about her and she fell in love with Eddie. He had a great life, though, living with her and Joe. She thinks he needs to stop thinking of other people and do whatever is in his heart.
Barry goes to see Harrison who tells him how it works. He has to use the particle accelerator and achieve the desired velocity or he'll die. He'll be creating a wormhole. Everyone talks and Barry decides to create a time machine. Cisco tells Eobard about remembering the alternate timeline and dude tells Cisco he was affected by the particle accelerator explosion. Cisco isn't pleased.
Stein chats with Eddie and realizes Eddie is feeling pretty down because of what Eobard said to him. He wonders why preserving and protecting Eddie was such a coincidence. There is no science to coincidence. He calls him a wild card. Stein says he's the only person who gets to choose his own future, making him the most important in the group.
There is a little snafu with the plan and that is timing. There is under two minutes to get 'er done. Barry can save his mother and get her home, but he can't stop Eobard from leaving and escaping to his own timeline. Barry wonders what Joe thinks now, and Joe isn't sure. Joe does think Barry is fast enough. Barry cries again. Barry was always so focused on what he lost that night, he never stopped to think of what he gained, a second father.
Eddie goes to see Iris. There were so many coincidences he forgot about all of them that lead to Iris. Screw the future. They're back together.
Barry goes back. He cannot save his mother. He sees himself, and he stops himself from saving his mother. He talks to her. She says he looks like her father.
Wow. Everything else went so fast! Barry got back and Eobard tried to leave, but Barry came trough the wormhole and a fight ensued. Because he was told he was the wildcard, Eddie shot himself in the chest, assuring that Eobard Thawne was never born. The wormhole, which was closed, opens again and Barry sets out to close it. AND THE CREDITS ROLL!!!