Disclaimer: I do not own Supergirl or anything to do with DC. I do not make any money from the writing of this story.
Author's note: This story takes place during Episode 13 of Season 1 of Supergirl.
*****
Alex Danvers hadn't been sure what to expect inside of her little sister's head. What she first found broke her heart a little. Then she thought about it and it broke her heart even more. Because the first thing she saw was Krypton, the home world Kara had lost years ago. Which should have been what she was expecting. After all, what else could it be?
For a moment there was a fleeting thought, and then Alex focused on all the people her adoptive sister had lost, including her biological family. Then she thought about what this really meant. That Kara was secretly so unhappy living on Earth, with Alex, that the only thing she wanted was to get away.
Of course Alex couldn't focus on her sister's happiness, or lack thereof, or how it made her feel, or anything like that because Kara's life was at risk here. Because in reality Kara wasn't on Krypton, she was in the grip of something called the Black Mercy, an alien plant which Kara's Uncle Non was using to try and incapacitate her, or worse kill her.
Alex only knew what it was because of a visit from Kara's Aunt Astra, who didn't want her niece to die, which would happen if Alex couldn't make Kara snap out of this dream-like state. Alex didn't even know how much time she had before the worst happened, but she was determined to save her sister. No matter what it takes.
Inside the dream Alex was still dressed in her black DEO uniform, and she even had her gun, which she took out for comfort, even though she wasn't sure it would have any effect on anyone she came across.
Luckily her training as an agent allowed her to avoid detection, although it was touch and go because wherever she went was filled with people who weren't Kara, and although most of them weren't carrying weapons there was no way she could guarantee they wouldn't be hostile. In fact it was more likely they were being controlled by the Black Mercy, and not Kara's imagination, so Alex avoided them while slowly making her way through the building.
She checked room, after room, after room until finally she found her sister. When she was sure there was no one else inside the room Alex cautiously opened the door, slid inside, and then close the door behind her. She then opened her mouth to greet the Kryptonian, only for her words to become lost.
Before she had been so grateful to find her sister that Alex hadn't really taken in what she was wearing, but now was very much registering and it was taking Alex's breath away. Because there, standing in front of the full-length mirror was her sister, in most beautiful white wedding dress she had ever seen. It even had her family's crest on the front of it, a detailed Alex only noticed after she stumbled forward a little to get a closer look.
"Alex!" Kara exclaimed, turning around when she finally noticed the other girl in the mirror, "What are you doing here?"
"I-" Alex tried to stammer, but that was all she got out before being interrupted.
"You know we're not supposed to see each other before the wedding." Kara grinned, running over and pulling Alex into a bone crushing hug, then pulling back and frowning, "And you're not dressed? Why are you not dressed? You're, you're not getting cold feet are you?"
After blinking a few times to try and clear her head Alex began again, "Kara, what are you-"
"Or are you just not wearing a dress?" Kara continued like she hadn't heard Alex's protest, "Are you seriously not wearing a dress? Cause I know you're a tomboy and proud, but we talked about this. I want to see you in that dress, and you know your mother will kill you if she doesn't get to see you in it."
"My mother?" Alex frowned, and true what Kara meant by that.
"Yeah, she wants to see you all dressed up too." Kara grinned, then softly adding while wrapping her hands around the back of Alex's neck and gently pulling her even closer, "So does everyone. Clark, Lois, Jimmy, Winn, J'ohn, both our families and even Cat is here for our big day. Which I know has to make you nervous, Rao knows I'm terrified, but it's what we talked about for a year now. Our wedding. It's finally here. And I'll be there with you every step of the way. So please, slip into your sexy little wedding dress and let's just do this. Let's get married! Please? You know I can't wait to become Mrs Kara Danvers."
If that speech wasn't mind blowing enough Kara lent forward and pressed her lips against hers as Alex's eyes went wide with shock. She hadn't been sure what to expect when she had insisted on being the one going into Kara's head, but Alex could have never imagined this would be her sister's idea of perfection. Sister! Alex had always wanted one, and have been grateful when she got it, but now it seemed like a dirty word.
Like this dream world had forever tainted it. And tainted her relationship with Kara. It was wrong. All this was wrong, and Alex felt dirty for enjoying the kiss even for a single second. And it only lasted a few, Kara then pulling back with a hurt expression on her face as she sensed something was wrong.
"Alex?" Kara frowned, "What's wrong?"
"It's... it's not real." Alex stammered.
There was a rumbling in the distance and then Kara softly asked, "What?"
"This isn't real. Nothing about this is real." Alex said firmly, finally committing herself to pulling away which caused another telling rumble, "Nothing but us."
Kara gulped and then softly complained, "Alex, you're... you're not making sense."
"It's a dream Kara. This whole world is a dream." Alex started to explain, stopping when the ground suddenly shook beneath her, prompting Kara to squeeze and grabbed hold of her to keep her steady. Alex continued, "We're not on Krypton. We are not getting married. Kara, we're sisters."
"Sisters!" Kara exclaimed, and then after another rumble she let go of Alex and almost laughed as she began, "I mean sure, we grew up together but we're not... that's just something we used to say to explain why we were closer than most friends, but really we just didn't want to admit what we really felt for each other. But then... things changed... and now we're going to get married and live happily ever after. So I guess this, this is a dream. My dream. Our dream. Alex, it's our dream come true. Why are you trying to ruin it?"
"Because it's not real." Alex said firmly.
"Stop saying that!" Kara practically growled in the middle of yet another rumble.
"What happened yesterday?" Alex pushed.
Kara shrugged, "Half our guests arrived, we all had a meal together, and then we went to sleep for the last time without being a married couple."
"No." Alex said, "You were attacked, by something called a Black Mercy."