Something that occured to me after re-watching Supergirl Season 4 and Smallville Seasons 7-10. Timeline-wise, this takes place post-Season 3 of Supergirl, with the exception of no Red Daughter being created by Harun-El. As much as I found the Red Daughter arc in Season 4 interesting, it doesn't work for this story.

Disclaimer: I do not own DC Comics or the CW TV shows Arrow, The Flash, Legends of Tomorrow, Supergirl or any other characters or elements pertaining to the mentioned franchises.

Brainy was in the lab as he turned around to face Lex Luthor. "No. No." He stepped back, shaking his head before firing a beam from his ring, obliterating Lex as he sighed in relief. "Finally. It's over."

"It'll never be over."

Brainy paled as he whirled around to face Lex again as he stepped back in horror. "H-How…" Lex laughed. "I killed you. You can't be here. I swear, if you hurt my friends…"

"You'll do nothing. Because you can do nothing." Lex gloated.

"No." Brainy stepped back, shaking his head and holding it. "No! Just leave me alone! Leave my friends alone!"

"Hand over Myriad and I will…"

"Never. I'll stop you." Brainy fired some energy blast from his hand but went straight through Lex.

"Brainy, what are you doing?" Alex demanded.

Brainy turned around to face her before turning to Lex again, who laughed. "Poor Alex."

"No!" Brainy glared, pointing at him. "Leave my friends alone!" He whirled on Alex. "Alex, run!"

Stryker's Island

"There's no way he could've escaped." The warden said, accompanying Supergirl and J'onn down the corridor, opening Lex's cell as Lex got up, smirking.

"Supergirl. Mr. J'onzz. To what do I owe this visit?" Lex smirked.

Supergirl took a breath. "Mr. Luthor, have you been recently to DEO?"

"No. I assure you, I haven't left this prison in five years." Lex smiled as Supergirl turned to J'onn, who checked Lex's mind.

"He's telling the truth." J'onn said.

"If Lex was here the whole time, then who…"

DEO

Brainy glared at Lex. "I swear, if you as much as lay a finger on her…"

"Brainy, stop! Please, stop! There's nobody there, it's just you!" Alex cried out, tears filling her eyes as he turned to her.

Brainy snorted, shaking his head. "No. That's impossible." He turned around only to notice that "Lex" had vanished. "He… he was right here. I saw him. He must have used some device the instant you entered-"

"No." Alex shook her head, staring at her friend in worry. "I've been watching you for a while and the whole time you've been shouting at the air. Stop!"

"No. No, he must have used something to-"

"Brainy, it's gonna be OK, we're gonna figure this out, OK?" Alex said before her comms went off.

"Alex, is Brainy there?" Kara called out.

"Yeah. And there's something wrong with him, he's been talking with Lex…"

"But he's not really there, is he?" J'onn realized as Alex nodded. "We just checked in with Stryker's Island. Lex hasn't left the prison and there's no way he could've compromised DEO somehow, they've had him on constant surveillance the whole time. I'm not sure what's going on with Brainy but…"

"It's all in his mind." Alex realized. "What's happening to him?"

"I think we have a pretty good idea. Alex, run. Get as far away from him as possible." Kara said as Brainy was falling on his knees, sobbing, as if he was having a breakdown.

Alex neared Brainy, holding him by his shoulder. "Brainy. It's gonna be OK. We can help you."

Suddenly, Brainy got up as he stopped sobbing and he turned around to face Alex and as she looked into his eyes, the look he was giving her was chilling, as she immediately realized that there was something very off about him before she realized that she had seen that cold look before as she paled, realizing who was she facing. "Oh, my God… you… no… not you. It can't be…" She shook her head.

"You're in my way." "Brainy" said darkly as Alex breathed out, horrified.

National City

Kara and J'onn were flying in the air before she stopped. "Kara. Is everything OK?" J'onn asked.

Kara paled. "Alex." She tapped her comms. "Alex. Alex, are you there?" She then tried to switch channel. "Nia. Alex isn't answering my calls."

DEO

"I'm going to check in on…" Nia stopped as she entered the lab and gasped, stepping back in horror as she saw Alex lying on the floor with a glassy look in her eyes. Nia neared Alex, measuring her pulse before she broke down in tears, sobbing as she closed Alex's eyes.

So, what do you guys think? Is it good? Is it bad? Should I continue?

Please review and let me know if you have been enjoying this.

With regards

Bl4ckHunter