Let me very quickly say that this story has no relation to my now deleted work of the same title, it was just the most fitting title I could come up with. This is just an idea I've had for a bit, the original idea was very different but ultimately, this was the only way the story could work without being too convoluted.

As the summary said, Earth-1 and Earth-1999999 (the MCU earth), are one here. The end of Infinity War happens at the exact same time as Barry going into the Speed Force prison. I know it doesn't match up with the MCU timeline but just go with it.

Aside from Flash happening as it did in canon, Arrow and Legends have a few differences. 5x23 happened exact the same except Oliver managed to disarm Chase and restrain him, so he was locked in Slade's old cell when the snap hit and no island explosion. For Legends, everything is the same until Mick joins the Legion of Doom. Rather than joining them, Mick instead handed the Spear over to Sara, so they stopped the Legion without breaking time.

And that's pretty much everything you need to know. Onto the chapter.

Central City

Night

Heartbroken, Cisco, Iris, Joe, Wally, Julian, Harry and Jay all stared at the spot where Barry had walked into the Speed Force, disappearing from sight and from the earth, taking the lightning with him. They all stared, struggling to process what had happened when, suddenly, something no one could explain happened.

"What in the name of-" Jay exclaimed as they all stared, shocked as Julian just disappeared, turning into dust.

"You all saw that right?" Joe asked before, to their shock and horror, his left arm turned to dust followed by the rest of him.

"Dad!" Iris exclaimed in horror.

"What's happening? What's happening?!" Wally exclaimed, looking to Cisco, Harry and Jay for answers but the three of them looked completely lost.

Iris looked down at her hands, seeing they were turning to dust as well. She looked up as Wally realized what was happening but it was too late. She turned to dust in front of them as well.

Wally suddenly stumbled and would have fallen if Jay hadn't caught him.

"I got you Kid," Jay told him.

However, to everyone's horror, Wally turned into dust as well, disappearing in Jay's arms.

"What's happening? What's happening?" Cisco asked in shock and horror.

Neither Harry nor Jay had an answer, as confused and horrified as Cisco.

Lian Yu

Same time

The sun was just beginning to set on Lian Yu and things were wrapping up. Chase had been dealt with; he would spend the rest of his life in the cell Slade had once occupied. Speaking of whom, Oliver thought as he eyed his former ally thoughtfully, he still had yet to figure out what to do about Slade. Slade had betrayed him, tormented him for the better part of a year, killed his mother and tried to kill so many more people Oliver cared about. And yet Slade had helped him save the people he loved, including his son. Oliver was having trouble reconciling the two pictures of Slade - one a homicidal maniac bent on destroying everything Oliver loved, the other his closest ally who had kept him alive - in his mind.

Oliver was broken out of his thoughts by a scream piercing the air. William's scream, Oliver realized with a start. He quickly rushed over to where his friends and family were gathered, only vaguely aware of Slade behind him. William was staring, horrified as everyone else seemed shocked. Even Nyssa looked completely blown away. Samantha was missing, Oliver realized.

"What happened?" Oliver demanded.

"Samantha, she just…disappeared, right in front of us," Diggle said in disbelief.

"She disintegrated," Felicity corrected in shock.

"She's not the only one," Curtis said and they looked to see his hands beginning to disintegrate. "What's happening?"

Curtis turned to dust, which then fell to the ground before any of them could say a word.

"What the frak?" Felicity muttered before she to turned to dust, to everyone's horror.

"What in the Hell is-" Diggle had turned to dust as well before he could finish, followed closely by Dinah and Rene.

"What is going on?" Slade wondered out loud in shock but Oliver had no answers, simply staring in disbelief as he processed that his team was suddenly gone.

"Son of a bitch," Quentin muttered before he turned to dust as well and Oliver heard a sound that made his heart clench.

"Ollie," Oliver whipped his head around, seeing Thea stumble towards him.

Then started to fall but Oliver quickly rushed forward, catching her, the two of them falling to their knees.

"It's gonna be okay, you're gonna be okay Speedy," Oliver said desperately as he lowered her on her back to the ground, in denial, refusing to believe…

"Ollie…it's okay," Thea said, her eyes full of tears as she accepted what was happening. "It's okay."

To Oliver's horror, Thea then turned to dust as well, the dust particles flying up into the air. Oliver looked down at his hands, expecting – hoping, wanting, dreading – that he would turn to dust as well. But nothing happened, he was still there.

Behind him, William had tears running down his face, looking like the world had come to an end. Oliver wished he knew what to say but his mind was still struggling to grasp what had just happened. Slade looked like he couldn't believe what had just happened, a feeling that Oliver shared. But Nyssa, her face was set in a look of grief realization.

"Someone has done something," Nyssa declared. "This is dark magic; my father told me stories of such magic when I was a child. Someone is responsible for this."

Oliver did not respond, simply sinking to his knees, the losses hitting him all at once. Silently, Slade walked over and placed a hand on his shoulder. Oliver did not have the energy to decide whether he wanted Slade's comfort or not, so he just took it, allowing a long severed brotherhood to be reforged.

Wakanda

Same time

Steve Rogers, on his knees, turned over Vision's body, the gaping hole where the Mind Stone had once been a painful reminder of his failure. Behind him, Thor, Bruce, Rhodey and Rocket stood as Natasha raced up to his side, staring in horror. The absence of Bucky, Sam, Wanda and T'Challa weighed heavily on Steve's heart, like a thousand tons of bricks chained to his limbs.

"What is this? What the Hell is happening?" Rhodey asked and Steve's legs gave out and he fell into a sitting position, everything finally hitting him.

"Oh God," Steve said shakily. "Oh God."

Waveridder

The Legends were celebrating their defeat over Thawne, Malcom, Darhk and the time displaced Snart when an alarm blared.

"What's going on?" Jax asked.

"Gideon," Sara called out and the familiar holographic head suddenly appeared in the middle of the room.

"A massive temporal anomaly has been detected in 2017," Gideon informed them.

"What kind of anomaly?" Ray asked.

"In May, 2017, half the earth's population turned into dust," Gideon said and there was a silence that stretched across the ship that made the phrase 'you could hear a pin drop' seem like an understatement.

"WHAT?!" Sara exclaimed once she had found her voice.

"In May, 2017, the alien warlord Thanos arrived on earth and used the six Infinity Stones to wipe out half of all life in the universe," Gideon explained.

"We have to go back; we have to stop this from happening!" Nate exclaimed.

"We can't!" Ray argued and they all looked at him in shock. "If the people who built the Waveridder had ancestors who were affected by this Thanos, then the Waveridder could blink out of existence the moment we leave the time stream."

"Mr. Palmer is right," Rip agreed. "We have no idea what may happen once we leave."

"So we're stuck here until we die or someone fixes this?" Mick asked annoyed.

"Pretty much," Ray said with a sigh.

The Speed Force

In the Speed Force, in a scene that resembled Star Labs, a red haired woman in a red jacket stumbled into the cortex, falling to her knees.

"Welcome, Wanda Maximoff," Wanda looked up to see a red haired woman, several years older than her it looked like, standing a few feet from her. "We have been waiting for you."

"Wh-who are you? What's going on?" Wanda said, remembering her body grumbling to dust. "Am I dead?"

"You're physical body is no more," The Speed Force confirmed. "But you are not dead, not yet."

"Where am I?" Wanda asked, confused about what was happening. "Is this Heaven…or Hell?"

"Neither. We are The Speed Force. And we need your help Wanda," The Speed Force said, confusing Wanda greatly.

Well, that was painful. It wasn't difficult for me to dust Julian, Iris, Felicity, Diggle or the recruits, but Joe, Wally, Quentin and Thea were hard. But for the plot to work, Oliver and Cisco both need to be alone, to have huge motivations for what happens next. Everyone who was dusted in the MCU was dusted here and the fate of other Arrowverse characters will be revealed in the next few chapters.

Kara will not be showing up, as this will be a Flash/Arrow/Avengers story, which doesn't leave much room for her in it.

Wanda in the Speed Force is probably confusing, but it will explained and it's an important plot point for the rest of the story.

Before I forgot, the scene with the Legends was taken and edited for my story from Raptor2216's story 'Crisis on Earth-99', which they generously allowed me to use. So thank you to them.