The team allows Barry to have a talk with Wells he has been waiting to have for years. "What? No Big Belly Burger?" Wells wonders and he goes on about how in the future, there are no cows. Barry just goes straight to the point and asks the biggest question he has been wondering for over fifteen years.

"Why did you kill my mother?" Barry asks him and waits for the response. "Because I hate you. Not the you from now, the you years from now. In a future. We're enemies, rivals, opposites, reverses of one another. But that doesn't matter anymore. What matters was that neither of us was strong enough to beat the other. Until I learned your secret, your identity. Barry Allen. And finally, I knew how to defeat you once and for all. Travel back in time, kill you as a child. Wipe the flash from the face of the earth, except the future you followed me back, and we fought." Wells goes on and explains how the two speedsters were in fact Barry and Thawne.

Wells also explains how when future Barry saved his younger self, Wells was so mad he killed his mother so he would never become the Flash. But in changing the timeline, he erased his speed from existence stopping him from being able to return to the future. He lost his connection with the Speedforce and that caused him to create the Flash again.

And he needed the Flash to get fast enough so that he could disrupt the time barrier so he could return home. Barry asks why he would allow him to leave and Wells gives him a choice he could never refuse, a chance to go back. A chance to return to that night his mother was murdered and stop it all from happening.

-

He informs the team on what he's offeri and they don't know what to do. "The rare opportunity to go back in time and right a wrong and save your mother's life...quite the paradox Harrison has presented to you, mr. Allen." Stein states to him.

"The chance to save someone you wish you had more time with?" Peter asks since he knows how Barry feels about loosing his parents. "But there are still consequences, aren't there?" He states since he knows every time travel movie to exist since he has no real life and an aunt who loves movies.

"Of course, mr. Parker, this gift has an unparalleled risk." Stein agrees with Peter. "Barry, the night your mother died,the night you saved your younger self from death, that event altered the timeline you were already on and changed the course of history." Stein explains and they never realized that before.

"So it's like Terminator 3. We're living in an alternative world, part of an alternative timeline. A parallel universe." Peter states and wonders what his life would've been like in the previous timeline.

"But Barry changed one day once." Joe remembers when Weather Wizard was supposed to kill Peter, kidnap Joe and everything else.

"Yes, now imagine 15 years of compounded experiences. One different decision, no matter how big or small, impacts everything that follows. In physics, it's referred to as the domino effect. Moments upon moments, choices upon choices. New relationships, nothing would be as it is today, and you'd never know the difference because you'd never remember any of it." Stein explains to them and now it's up to Barry, it's his decision.

"So if I go back and save my mom, my dad doesn't go to prison. I never live with Joe and Iris." Barry lists some of the pros and cons. "You might never meet me. Or Caitlin or Ronnie. Peter might still be living in New York, he might not even become Spider-Man." Cisco lists some of the bad things to come with it.

"There's no real way of knowing what will happen until you do it." Peter explains as he seriously doesn't want to loose his abilities or what he's done to be erased from the world.

Joe and Barry leave to talk in private and the others just give them some space, and Barry decides to let his father in on the decision as well.

Stein and Peter just go into a private conversation about how the physics of time travel actually would work. Peter believes that once Barry changes the timeline, he'll create a new branch of time and once he returns to his time, he'll be part of the new timeline. Stein believes that once changing the past, it'll ripple throughout the timeline, the original timeline, causing everything to change.

Caitlin is checking on Ronnie to make sure he's okay. "98.6. Normal." She states taking his temperature. "I'm not sure I know what that means anymore." Ronnie replies to her and she agrees.

"I know Barry and Peter appreciates you coming back to help stop Wells." Caitlin tells him and he explains that's not the only reason he returned and he's back to stay this time.

"Once upon a time and a particle accelerator or so ago, you agreed to marry me. What do you say we do that?" Ronnie asks her and Caitlin doesn't know what to say.

Caitlin just looks to see Stein and Peter are still discussing time travel while borrowing the chalkboard explanation Doc Brown used to explain to Marty McFly in Back to the Future ll and she remembered that the Caitlin Snow that agreed to marry Ronnie a year ago isn't the same one she is now. She has changed, she's moved on. She's fallen in love with somebody else. She can't deny it anymore, from herself at least. She's fallen in love with Peter Parker.

"Ronnie, you know that I will always love you. But when I thought you died, I was moving on. When you left, I finally found a way to move on. I'm sorry, Ronnie, but I don't love you the same way as I once did." Caitlin tells him and he's shocked at first but Ronnie starts thinking of everything he put her through the past year. He died, then he came back, and then he left her again. He understands why she needed to move on, besides he doesn't know when Eiling will track them down.

"I understand, Cait." Ronnie tells her and she's relieved that he isn't freaking out like she thought he might.

-

Barry comes back and has made his decision. He's going back in time to save his mom. Wells explains that in order to do this, they need to turn on the particle accelerator. Except Wells redesigned the accelerator to work as it should have the first time, except Barry has to inject one particle and Barry has to collide into it and needs to go at the right speed in order to go back.

In doing so will create a wormhole that'll connect each timeline from past to the future. Except if anything goes wrong, Barry will die along with the city.

"According to Wells' calculations, Barry super speeds inside the accelerator ring. Once Barry reaches optimum speed, we then launch a hydrogen proton into the accelerator." Stein explains going over the calculations himself and shows a presentation to explain his point.

"So once the collision happens, a wormhole will be created, sorta like the Star Trek reboot, and it'll open a gateway into time itself." Peter finishes, seeing what the professor is saying.

"It's at that moment I plan on shouting something along the lines of "eureka" or possibly "excelsior". I'm uncommitted." Stein finishes to them.

"What do you guys think?" Barry asks, looking to Cisco and Peter, knowing they're not onboard with this.

"I mean, on the one hand, it does make the kind of sense." Cisco tells him.

"On the other hand, Here's a simple question. Why?" Peter asks, since he doesn't understand this anymore. This isn't just one life, this will effect the lives of everyone. "Why are we considering this?" He asks Barry.

"Peter, you know why." Barry informs him.

"Barry, there are four moments that have effected my life forever. My parents dying, getting bit by that spider, my uncle dying, and becoming Spider-Man." Peter recaps every moment that changed him. "If you change those moments, if you find that Peter Parker, you won't know that man." Peter warns him not wanting to change who he is because of his friend.

"For this to even work, how fast would Barry need to be going?" Caitlin asks Stein, hoping for some good news.

"By my calculations, Mach 2 at a minimum. And if he doesn't reach that, it's unimaginable how gruesome it'll become." Stein answers her and they know Barry has never went that fast before.

"I'll worry about the speed, but I need the two of you to work on something." Barry tells Peter and Cisco. "Really? And what's that?" Cisco asks since the two of them have shown no interest in this project. "I need you two to build a time machine." Barry tells them and they become very interested.They go into the labs to start working on the machine.

"So if Wells is as fast as Barry, what's he need a time machine for?" Ronnie asks them as he decides to help his friends. "Apparently, when he changed the timeline, and unsurprisingly, it changed him and he lost his speed and only gets it back sometimes. It's like when your tv starts fizzing in and out." Peter explains to him. "Which means I was right about the wheelchair. He was using it to charge himself." Cisco states to them happy he was right.

"And that just means that after Barry opens a wormhole, he's gonna need a ship to send him back to the future. He's been hiding the parts around the labs, and it juts needs to be put together." Peter tells them and now they know they need to talk to Wells about the dust the pieces have collected over the years of being hidden for years.

Cisco is with Wells as he looks over the blueprints as he realizes something is bothering Cisco.

"Something on your mind, Cisco?" He asks him wondering what's bothering him.

"Yes, how did you fit your Reverse Flash suit in that ring? Is it some compression micro tech?" Cisco asks and realizes it's not important.

"Ronnie's right. I should've accounted for the temporal shearing. I never underestimated your contribution, Cisco. Or Ronnie and Peter's. As a matter of fact, do you know how many times I wished you all were there with me as I rebuilt the accelerator, it would've been more fun with you and Peter." Wells tells him.

"Well, doesn't change the fact that you're Time Sphere is gonna blow." Cisco tells Wells and he tells them how to prevent the explosion and Cisco leaves to try it.

"Is that all you wanted?" Wells asks as Cisco walks off and turns back to him.

"Well, what do you want me to say?" Cisco questions the mad man.

"I thought of anyone, you'd be a little more understanding of my predicament. I don't belong here. These barbaric times. It's like living amongst the dead." Wells explains since everyone here is dead in the 53rd century.

"Is that what you told yourself when me and Peter died?" Cisco wonders and Wells is confused by that statement. "It was an alternate timeline, one Barry fixed. One where Peter was killed by Mardon and where you called me a son and crushed my heart with your fist." Cisco expains and Wells is shocked to hear this.

"Cisco. I'm sorry you're able to retain traces of another timeline. You're able to see through the vibrations of the universe. That means when the accelerator exploded, you were effected, too." Wells tells Cisco and it's his turn to be shocked that he has powers. "Don't be afraid, Cisco. A great and honorable destiny awaits you." Wells promises Cisco and he doesn't want a destiny.

-

Later they have everything ready for Barry to go back. Barry is just saying his goodbyes to his friends and they know that everything changes when he saves his mom.

Barry says goodbye to Joe, Iris, Caitlin and Cisco and moves into Peter. "I will never forget what you did for me. All the nights we spent training, you helping me see things through a different persons perspective." Barry promises Peter and hugs his friend.

"I'll never forget you, padawan." Peter tells him even though if this does happen, he'll never have met. "I hope what life you have it was worth the risk." He says and they separate and Barry runs.

Barry remembers that Wells said he has one minute and thirty seconds, before a wormhole opens and destroys the universe so he has to move fast.

He starts reaching Mach speed and Wells tells him to remember that night, the night his mother was murdered. A portal is opened and Barry vanishes.

"I believe it's time to say goodbye to Harrison Wells." Stein states and they agree. They make it to the pipeline and release him and show him the Time Sphere.

"It's beautiful. Rip Hunter would be impressed. He built the first one of these things." Wells tells them when Peter's senses go off and watch as a metal helmet with wings on the side comes flying from the portal. "What the hell is that?" Peter asks what they're all wondering.

"That's my que to leave." Wells tells them and gets into the time machine and starts it up. "You do realize that we're the first people to actually build a time machine, right?" Peter asks Cisco and he just now realizes the same thing. "That makes some of this worth it." Cisco informs him when a flash of light exits the portal and destroys the Time Sphere. They look to see it was Barry, he's returned to their timeline.

"You didn't save your mother?" Peter asks, confused to how nothing changed. "Why?!" Wells asks, getting back up. "You could've had everything you ever wanted!" He states to Barry as he also stands up.

"I already do." Barry states to him when Peter realizes they need to shut down the portal before everything explodes and the speedsters begin to fight. He reaches up top and helps Caitlin and Ronnie who have the same idea in mind and shut down the generators.

Barry and Wells continue to fight as the portal closed.

"Just so that we're clear, after I kill you, I'm going to kill them, even your father. I always win, Flash." Wells informs Barry when a gunshot is heard and it shocks everyone as they see Eddie committed suicide to stop the Reverse Flash.

"Eddie!" Joe tells and questions his partner as they watch Wells shaking.

"What's happening?" Barry asks his team.

"He's being Marty McFly'ed. Eddie is his ancestor. If Eddie dies now, there will be no future bloodlines and...he's being erased from existence." Peter tells them and watch in shock as Wells turns into a older man with blonde hair revealing to the the real Eobard Thawne.

"I controlled your lives for so long. How are you gonna do without me?" Thawne asks before he let's out a nightmarish scream as he completely vanished.

"That image's gonna haunt my dreams." Peter promises when the portal opens back up and raises from the labs.

"It's reopening. The portals reopening!" Cisco warns everyone as they all begin running for it as the portal grows larger.

They all run outside and see the wormhole destroying earth. "I believe the end is near." Peter states to them as they hear citizens screaming and running from the portal. "What's it doing?" Caitlin asks them.

"Feeding." Stein starts explaining. "The singularity won't stop, not even after the earth is gone." He tells them.

In the distance, Snart looks up to see the portal, Curt Conners from Mercury labs sees it, Captain Singh notices it. Even Barry's dad in prison notices it.

"I'm afraid the accretion disc has already assembled. The diffuse material that's in orbital motion around the singularity." Stein tells them and then an idea enters Barry's head. "We have to disrupt the motion." He tells everyone. "Basically it's kust like the tornado, only in the air." Barry explains and they don't like that idea.

"Buddy, that thing has an energy level of Maybe at best 6.7 Tera Electron Volts." Peter informs his friend there's nothing they can do to prevent it. "I have to try." Barry states and is prepared to stop it and raises his mask.

Peter sees there are people being sucked up and he needs to help. "Good luck, Flash." Peter says and runs off and puts on his mask to save the citizens.

Barry begins running and leaps into the air and runs across the debris to use it to keep himself in the air. Everyone is grabbing on to everything they could to not get pulled in as Peter swings in and helps them stay on the ground or get them to a safer distance.

In the air, Barry keeps running as fast as he can to keep the singularity from destroying earth.

"He's contained the singularity by adding to its angular momentum." Stein tells them happy that its working, but it will only work for so long. "Now what?" Cisco asks Stein. "We have to merge the inner and outer event horizons." Stein explains the next part.

"How do we do that?" Ronnie asks him. "By separating in the eye of it." Stein explains and that means they have to get up there themselves, and there's a chance they could not make it back.

Ronnie and Stein merge and are ready to save the city. They fly off into the air into the eye of the storm. Barry keeps speeding around and sees them entering.

Peter is swinging around, helping the citizens when he also notices Firestorm flying into the eye. "No!" Peter and Barry shout when they separate, and the storm closes.

Peter sees Stein falling and leaps to catch him and swings him to the labs and hops Barry found Ronnie. They quickly make it and see Barry speeding up to them, but with no Ronnie. Stein starts waking up and looks around for his other half. "Ronald?" Stein asks the speedster and he's sad to say he's gone.

The team meet up and have the same question in mind. "I'm so sorry." Barry says and Peter moves to comfort her since they both lost someone special to them.