This is an AU Story
I DO NOT OWN Supergirl, Flash, Arrow, DC's Legends of Tomorrow, or any other DC related characters.
Timeline
The events of Flash Season 3, Supergirl Season 2, Arrow Season 5(Assuming William's mother didn't survive Lian Yu), DC's Legends of Tomorrow Season 2 all occurred in this universe. The only real difference is that they all transpired in the same universe. Only Earth 2 (Harrison Wells, Jesse Quick,etc) is the other parallel universe they know of.
Wonder Woman, Green Lantern, Batman, and Superman will also be in this story. Let's just imagine that they inhabit the same universe. The justice League was also formed after the Dominator Invasion so that the Earth could be defended from large scale. Every hero in the Arrowverse is a member. For story reasons let's say that the heroes were too overwhelmed with their own individual villains, so they couldn't help Supergirl with the Daxamite Invasion.
The following morning Kara would wake up to the smell of a fire.
She quickly rushed into action and used her freeze breath on the fire
"What the happened Mon-El?!" Kara furiously asked
"I was trying to cook breakfast for you, but the fire just all of sudden got out of control. I'm sorry I wasn't really taught how to cook in Daxam or in the future."
"That was very sweet of you, but maybe next time leave the cooking to the professionals." When she finished, she went up to him and gave him a quick kiss.
"Since we're both up what do you say we go get breakfast, I can invite Maggie, Hank, Alex, Winn, and James so they could see you're back." Kara said
"That sounds like a great idea" Mon-El said
After some phone calls, the couple got ready to meet their friends.
Before parting ways Kara received a text from Barry telling her there's a league meeting at the hall and that he's coming to pick them up.
Once they all reach the hall they're greeted by a brooding Superman.
"What's wrong Clark?" Barry asked
"He has her" he replied
"Who has her?" Kara asked
"Joker, he escaped Arkham yesterday. This morning when Clark arrived to work he found a note in his desk drawer." Bruce replied
He pulled up an image of the note for everyone to see and it read:
Muahhaha
It is me! The Joker!
I snuck into your workspace and napped Lois
all while you were so happily celebrating the return of your friends.
"Did you analyze the materials of the note?" Barry asked
"Of course, I wouldn't be the world's greatest detective if I didn't. The material was manufactured from a subsidiary of the once Luthor Corp now L-Corp in Metropolis." Bruce responded
"Flash, Supergirl you need to get to Metropolis and begin searching the building, there might be a clue to Joker's whereabouts and it's our only lead. Clark, you should stay behind you're too emotional right now, they can handle it. Bruce and I will follow another lead" Oliver said
"Ok" Barry and Kara responded.
"Don't worry we'll get her back" Kara reassured her cousin before leaving
Once done Barry quickly carried her to Metropolis and the two headed to the Building. Kara began using her x-ray vision while Barry zipped through the building.
"So, how's life with Mon-El now?" Barry reluctantly asked through the coms.
"Barry, were searching for evidence is this really the moment for chit chat? "Kara asked
"I know it seems like a bad time, but when you're the fastest man alive every second feels like an eternity, so I want to pass the time." Barry replied
"Fine, if you have to know life's great, I haven't felt this happy in forever, I finally have all I ever wanted" Kara replied
"Oh" Barry looked down. Even though he expected to hear those words, the truth still hurt him. "Just typical Allen luck, can't seem to get a break" he thought to himself.
Kara took notice of his silence, but before she could ask why he seemed disappointed they both heard screams.
The two headed to the origin of the commotion which was the park. The causes of the mass hysteria were Silver Banshee and Livewire.
"Aren't you two a little far from home?" Barry said
"We'll if it isn't the Flash, last we heard you took a vacation. You left Central city unprotected. We made some very memorable heists there." Livewire said
Furiously Barry began his attack. He easily subdued the two of them with his newly acquired speed.
"Well guess what? I'm back and faster than ever stay, stay away from Central and any other city." Barry said
"I'll take them to Strykers Penitentiary, you should keep looking. I'll be back in a flash." Barry said. With that he was gone. Kara slightly laughed at the bad pun and returned to her previous activities.
"So, anything?" Barry asked when he returned
"No, I can't see anything. It looks like a dead end" Kara replied
Barry sighed, "Ok, lets go back to headquarters, hopefully Oliver and Bruce made some progress." Once finished Barry's stomach growled.
"You know what, I saw an all you can eat buffet on my way back. Would you care to join me Miss Danvers?" Barry said holding out his hand.
"Yeah sure Mr. Allen as long as you pay" Kara replied as she grabbed his hand and he quickly took them to eat.
Elsewhere in Gotham
"Overwatch you copy?" Oliver said into his coms
"Overwatch here, I still don't understand why you didn't ask the rest of the team for help. John, even Rene could have helped." Felicity/Overwatch said
"This requires a more league of assassins approach. That's why Bruce and I are here" Oliver said. "Ok were going radio silent talk to you later."
"Bruce what's the plan? Your city your rules" Oliver asked.
"Follow my lead, the streets are filled with criminals who are willing to talk if you push them hard enough." Bruce replied
With that the duo went to work, interrogating any criminal they could get their hands on to ask for the Jokers whereabouts.
"That's the thirtieth. No one seems to know where the Joker is." Oliver said exhausted.
"Yeah, I still got one more lead, but we'll have to go to Arkham." Bruce said.
At Arkham
"So, who are we looking for?" Oliver asked
"Just a moment" Bruce replied as he waved someone to come over.
"Green Arrow, I'd like you to meet Commissioner Gordon. The commissioner is one of my most trustful allies" Bruce said. As he finished the commissioner held out his hand.
"Pleasure to meet you commissioner, it's good to see that some of us have the law on their side" Oliver said with his voice modulator.
"Ha, before I joined forces with Batman, he was public enemy number one. I was actually always trying to arrest him" Gordon said.
Oliver grinned
"Anyway, commissioner can we do the thing we discussed?" Batman said
"Yes of course right this way. We had to mover her, she's been quite unstable since Joker escaped" Gordon said.
"She?" Oliver asked
"Harleen Quinzel aka Harley Quinn, she's the Joker's main accomplice. She was a psychologist who was driven insane while taken care of the Joker" Batman replied.
"Here we are gentlemen I'll leave you two alone with her" Gordon said besides a highly secured cell.
The two men entered the cell and were greeted by a blonde woman in a straitjacket.
"Batsy Batsy, what have we here a new sidekick? I would have expected him to look a bit younger." She maniacally laughed "Guess you're tired of abducting young kids, we'll Bats whatever floats your boat."
Batman ignoring the sidekick comment said, "Enough games Harley, where's Joker? You always know about his plans so, where is he?"
"Sorry to tell you bats, but even I don't know. My puddin is in a whole other league of his own. He's planning something great so you better watch out. You and your superhero friends are in serious trouble. Just know the celebration of the Flash's return may be the last time you'll ever be happy in a long time. Remember one day, is all it takes to fall over the edge" Harley said. As she finished she began to manically laugh.
"Hmm bad day. Thanks Harley you may have just given me the clue that ties everything together" Batman replied. With that the two men exited.
"A bad day? Really that's the clue? I don't see how you got that from her little monologue" Oliver asked.
"I'll explain it later, but right now we have to get back to the hall" Bruce replied
In Metropolis
Barry and Kara were enjoying their little competition of who could eat more.
"No more please you guys ate half of all the food here" the owner of the buffet restaurant said.
"Sorry we got a little carried away" Barry replied embarrassed. "I'll just pay so we can be on our way" With that the two left before the owner could get more furious.
"So that was exciting, you know what I could still go for a Big Belly burger" Barry said.
"Umm maybe later, we still have to get back" Kara said.
Barry sighed and said "Yeah that's true, I'll carry you."
As they ran the two saw a horrible sight. A mushroom cloud was over Metropolis.
Barry barely had enough time to run them away from the blast zone. He and Kara stared in shock at the destruction. The Metropolis skyline was replaced by a wasteland.
"Overwatch something happened. A nuke seems to have gone off." Barry said into his com
"Damn it, Kara you're the only one who can find survivors in the city the radiation shouldn't affect you. Barry do a perimeter search see if there were any survivors."
"On it" they both replied
As Kara entered the blast zone she surprisingly found Kal-El crying besides the ruins of the Daily Planet. He was crying. She couldn't help but cry besides Kal-El.
"Kara promise me you'll always be with me"
"I will Kal-El, you'll always be my little one"
"Thanks Kara there's something I got to do" He flew up into the sky determined to find the man who took his city from him.
Meanwhile in Gotham
Oliver and Bruce had decided to keep tracking down the Joker, once they heard of the devastation in Metropolis. by themselves. They managed to track him down to the infamous Ace Chemicals. The facility seemed dead silent. The two-stood outside.
"Is it usually empty?" Oliver asked
"Yeah it hasn't been operational in years" Bruce replied
After the statement, a projector turned on. It showed a man in a purple trench coat, with pure white skin and green hair aiming a toy gun at a tied-up female. He pulled the trigger and a small "Bang" flag exited the end. He laughed.
"Bats I know you're there, come in alone and I might just let the poor woman here live" He finished with a maniacal laugh and the projector turned off.
Before they could discuss a plan, one blue streak passed them and headed in the building. They head in to find Superman freeing the unconscious hostage.
"Where's Joker?" the archer asked
"He's where he belongs" Clark said pointing at the corner where scorch marks were present.
"What did you do?!" Batman angrily asked
"I did what you never could, I ended that bastard's life so he won't be able to hurt another living soul. It's kind of poetic, he died in the same place where he was created."
"Clark, we need to discuss your action, I know you're grieving, but you didn't need to kill him"
"That's where you're wrong Bruce, I just spared countless lives. I've been playing hero, when I should have been judge, jury, and executioner. I can save others from suffering like I did. Think about it, a world free a crime. Bruce no one will have to live through what happened to you. Join me both of you, help me make the world a better place" Clark held out his hand
"No" the two men replied
"NO?!" An irate Superman replied
"If you're not with me, then you're against me" The Kryptonian lit up his eyes and fired at the two men. Only the archer's bow remained. The Kryptonian gather his thoughts to explain how the two "died" while he carried the unconscious woman to the hospital and began flying to the Hall of Justice to recruit others to his cause.
Unknown to him, Barry had arrived just in time to save his two friends. He made sure to run faster than Kal-El could see and carried them both to the Arrow Cave.
"Oliver, Bruce what happened back there?"
"He's gone mad" Oliver replied
"We need to tell the rest of team" Barry said
"And put them in jeopardy? He's too strong for all us to fight him. I doubt Kara will turn on his own cousin. Diana admires Clark, she'll most likely side with him. You're our only hope Barry" Bruce said
"Me?" Barry pointed to himself
"Yes, think about it. It's basic science you have the ability to generate great force with your speed. You may be the only one able who can incapacitate him. You could run at light speed and beat him with a single punch before he can react"
"I'm nowhere near that speed"
"You can with enough hard work. I have an underground bunker where you can train and from where we can operate from. It has enough supplies to last us a decade. It's located here in Star City. Oliver and I can go there, while you go back to the hall of justice. Gain his trust, convince those you trust to our side, and when the time is right we strike"
"Fine, I'm going back to the hall to do it." With that Barry left.
"Bruce give me a minute I got to make a call" Oliver said
Barry would arrive back at the hall to find everyone mourning their two "dead" members.
Clark cleared his throat "We'll give them a proper burial tomorrow"
"I hope the bastard rots in hell." A crying and furious Felicity said.
Barry made a mental note to tell her later about Oliver being alive.
"Barry we're glad to see you finally join us." Clark said
"What happened, who's dead?"
"Oliver and Bruce, they we're both killed while at Ace Chemicals, the Joker seemed to have set the building to blow, I couldn't save them. I did end the Joker's life so he won't take any more lives." Clark said finishing the statement with tears
"Man, this is my fault I should have been there, I could have saved them" Barry said to make the others believe he blamed himself. He even shed tears to make his performance believable.
Kara came up to him and hugged him. I can get through to her, she's a good person, she's not as far gone as Clark he thought
"Well I think we've had enough loss for tonight, lets meet up here tomorrow to burry our friends." Clark said
"Yes" everyone said and before long the hall was empty. Except for Kara, Mon-El, and Barry.
"Barry, can Mon-El and I come to your place we want to be there for you we know how much Oliver was like a brother to you"
"Sure" he answered while sobbing "I have a guest bedroom you guys can stay there"
He carried both of them to his apartment before they could react and went to his room and fell asleep.
