Disclaimer: I don't own Supergirl or the characters. This is written purely for fun.

A/N: This is set in Season 4 several weeks further ahead than the show is now. As such there are a few assumptions:

1. The other version of Supergirl has emerged and by pretending to be Supergirl when committing evil acts the city and Alex believe that Supergirl has turned.

2. The mind wipe has continued to have unexpected consequences and Alex and Kara are drifting apart.

3. Lena has found out that Kara is SG and has not taken it well. Their friendship is in tatters and Lena has become isolated.

Despite all of the above and the events of the first few chapters this will have a happy (ish) ending.

"Hey guys, what are you doing her?" Alex asked when she found J'onn and Kara waiting on her doorstep.

"Alex, we need to talk to you." J'onn said.

"Sure, what's up?" Alex asked letting them in.

"It's about Supergirl."

"What about her?" Alex asked wearily.

"She's not the enemy." J'onn stated.

"Isn't she? Because when people start killing my Agents I see them as the enemy."

"That wasn't Supergirl." Kara said.

"It sure looked like Supergirl, sounded like Supergirl and had Supergirl's powers. So my money is on Supergirl." Alex argued.

"Supergirl wouldn't do that." Kara argued.

"Only she did. And it's not the first time she's gone off the rails. I have a break in my arm thanks to her." Alex remind her almost causing Kara to flinch at the harshness of her words.

"What happened back then was a result of Maxwell Lord, it wasn't Supergirl's fault." J'onn said.

"Maybe, but it was a warning of how dangerous she could be. A warning we all ignored. And because we ignored it people are dying." Alex said.

"It's not her. There's another explanation." Kara said.

"Like what? A twin sister? Her version of Reign?" Alex asked. "No if there was ever an example of Ockham's razor being needed it's here. The simplest explanation is Supergirl has turned."

"Think about it Alex, why would she?" J'onn asked.

"Perhaps her ego took a hit when the President showed she wasn't vital to the DEO?" Alex suggested. "Or perhaps she is high on some crazy Kryptonite. Or maybe she got disillusioned by the Children of Liberty. All I know is she is a threat and we need to stop her."

"Supergirl is not responsible and she is not the enemy." Kara said.

"Kara, you don't understand." Alex said. "This is what I do. And I'm good at my job. So how about rather than trying to push your beliefs onto me, you trust my judgement."

"You really believe that Supergirl is responsible?" Kara asked looking Alex in the eyes. "That she's a killer?"

"Yes." Alex said with no trace of doubt in her voice. The answer feeling like a punch to Kara.

"Well there is no point in talking about this further." Kara said trying to hide how upset she was. "I better go. And Alex, I have an assignment out of the city so I won't be around for awhile." With that she hurried from Alex's apartment.

"Kara, wait." Alex called but when the door shut she looked at J'onn and asked.

"What's up with her?"

"She knows Supergirl is innocent and she wants you to believe it."

"Then bring me proof." Alex said. "You know I trust your judgement, but I also trust mine. And right now I have no reason to believe Supergirl hasn't turned."

"Alex, just promise me you won't do anything you'll regret. Killing is never the answer." J'onn said.

"You didn't use to feel like that." Alex said. "I will do what it takes to keep this country safe. And right now that includes stopping Supergirl, by any means necessary."

-00-

"You okay?" J'onn asked when he met Kara by his car.

"Yeah." She said, but as J'onn kept looking at her she shook her head and said. "No."

"Come here." He said pulling her into his arms.

"Was any of it real?" Kara asked.

"Of course it was. Alex loves you."

"Well she hates half of me." Kara said pulling away.

"She doesn't hate Supergirl." J'onn said. "But she has lost faith in her, which is why I think you should leave."

"I just told Alex I was going away for awhile."

"As Kara. I mean both parts of you should stay away." J'onn clarified.

"I'm not running away."

"The DEO are developing weapons that can kill you with a single shot."

"I know that. But although Alex has lost faith in me, I still have faith in Alex. And I'm not leaving her unprotected when there is an evil me running around out there. Besides anyone who wants to can get a gun that could kill Alex with a single shot. She has always had my back and right now whether or not she is willing to accept it she needs me to have hers."

"Okay, just promise me you'll be careful." J'onn asked.

"I promise." Kara said.

"Something else on your mind?" J'onn asked.

"I get her not liking Supergirl. I mean it hurts, but I kind of get it. But I had hoped by now we would have started connecting again."

"The other you isn't helping with that." J'onn said.

"I don't mean Supergirl and Alex, I mean Alex and I. Every day we drift further apart." Kara said sadly.

"You are keeping your distance as much as she is." J'onn reminded her.

"I'm keeping my distance to stop her figuring out who I am and to her allow herself to get everything she wants. She's keeping her distance because she wants to. Do you know when we last had a sisters' night?"

"No."

"Neither to I. I miss my sister." Kara said sadly as her phone buzzed. "I have to go." She said having read the message.

-00-

"Where have you been?" Nia asked when she opened her door to Brainy.

"At work." He replied. "My absence would be noticed, even when I multitask."

"I know. I'm sorry. But I need your help and I don't know if I should tell Kara. I mean I know I should, but it'll break her." She said pacing.

"Break her?"

"Well how would you feel if your sister killed you?"

"Alex is going to kill Kara?" Brainy asked eyes wide.

"Yes. No. I mean I don't know. I had a dream that Alex killed Supergirl."

"This is bad." Brainy agreed. "How did she kill her?"

"She shot her. It was a gun I didn't recognise, but that could have been symbolic. I still suck at this interpretation thing." Nia said. "Should I tell Kara? I mean she is going to get so upset and she is already upset."

"No." Brainy said. "Don't tell Kara. I will work on something. For now just tell me everything you saw. No detail is too insignificant."

-TBC...

A/N: Thanks for reading and reviewing.