It's been a week since she's seen Barry. Iris is slowly losing her mind.

She's at the office because home doesn't feel like home without him, and she can't face another day of looking at her dad and telling him Barry's not home. He is somewhere, he is somewhere, he is somewhere.

I'll always come home. (Kisses her goodbye, squeezes her hand lightly before letting it go, reaching for the door.) I love you. I'll see you soon.

As far as last words go, they're hard to swallow, and Iris inhales deeply to calm herself.

Barry will come home. He always does.

Even when he chases the impossible, he shows up eventually, breathless, exhilarated, but sobered, like there's something about the pursuit that's missing. She asks him what it is and he never has an answer, only a vague, intangible, I just feel like I should be more involved.

Barry. You're a reporter, not a superhero. You can't save everyone.

I know. (Hovering over her, knees bracketing her thighs, and she runs her hands up his sides just to feel him shiver.) But I want to.

Don't get hurt. (A whisper as she cradles his head, draws him in for a kiss that neither of them keep track of, and the simple press of his body against hers is like forgiveness.)

It's been a week since she's seen Barry.

And Iris is starting to worry.

Staring out at the stars over Central City, barely visible through the air pollution, she thinks, Come back, Bar.

. o .

Iris is at the precinct and it's quiet up here, her hands shaking with fatigue as she clicks away at her laptop, occasionally pausing for a sip of the coffee beside her. Midweek has been slow, tedious, which gives her too much time to think about him. Out of sight, out of mind only applies to certainties, things you expect to resolve peaceably.

She can never quite banish him from her thoughts because there is no certainty. When Barry vanishes, she can only hope he will return.

There are footsteps, careful, methodical, and Iris stills, her heart skipping a beat as she presses save and closes the document. She can already feel the tears, the hot wave of relief sweeping over her as she logs out of her computer with trembling fingers and stands, turning on legs that scarcely want to oblige to face him.

He is as beautiful as she remembers him.

"Barry," she breathes.

The way he walks as he closes the distance between them is so familiar it makes a tear slip from her hold. He looks at her like she is supernovic, something awesome and destructible, capable of profound changes. He treats her like she is one of his equations, something beautiful and intangible. As if she is an escalation that makes even his endless mind spin, always seeking bigger ideas, expounding on paradoxes, and trying to play with science that doesn't exist yet, to persuade her to see his point of view.

He's looking at her with such soft eyes, and she missed him, she missed him, she missed him.

There's a moment when he opens his mouth to speak but before he can do more than exhale she takes him by the lapels of his coat and kisses him hard.

Eyes closed, she feels his deep inhale, not sharp enough to make her pull away, but heavy enough to be noticeable, chest flexing underneath the palm she keeps flat over his chest. His heart is racing and she thinks, This isn't like you. But it's him. It's Barry. Barry's home.

Why are you so scared of me?

But he slides his arms around her back like he knows her and some of her trepidation vanishes as she presses back against him, tries to hold him there forever. He knows her. He knows her as well as he knows any of his passions: incompletely, but somehow more perfect for it. Like she'll always surprise him, to his very last breath, and he kisses her like he's hungry for it, like it'll be the last breath of air he will get for a very long time.

And she thinks, Where are you going, Bar? as she tangles her fingers in his hair. Why are you leaving?

Then he shifts his weight, hesitates, pulls away until she can just feel his breath against her lips, and there's a shakiness to it. Like he's breaking a rule. Like he's in trouble.

She knows him: how he breathes, how he moves, what he smells like in a fresh set of sheets. She knows what it feels like when he laughs against her. She knows how he can take her in his arms and make her feel safe, and she knows what it feels like when he comes home.

In spite of everything – the euphoria at seeing the familiarly friendly, sheepish smile and the raw relief at watching Barry walk into the room, unharmed, under his own power, because I could never live with myself if something happened to you – or maybe because of it, she knows, Something is wrong.

She pulls back, looks at him, and there's a breathtaking sadness in his eyes that bothers her, and she knows she's frowning even though she should be smiling because he's home.

But this isn't Barry.

She reaches up, holds his chin, forces him to meet her gaze, and she can't read him at all.

"You're not him," she says, very softly, as she releases him. "Where is he?"

Barry – not-Barry – exhales slowly. "I don't know."

Iris grips his jacket, hard. Anger is emerging, shattering the stoicism. "Who are you?"

"It's a long story," not-Barry replies apologetically, and he's got his eyes, and Iris is trying to be angry but her heart is also breaking because it isn't Barry.

Barry is still missing.

"I have a theory," not-Barry adds, swallows hard, shuts his eyes. "I think – I think Zoom took him."

Something in Iris' heart fractures.

She tries and fails to imagine him in Zoom's captivity.

Her sweet, sunshiny geek. A man who literally trips over his own feet but still pulls together brilliant insights for his groundbreaking, somehow perpetually ignored articles: targeting meta-human activity, seeking answers, trying to keep track of all of it, always wanting to be involved. He's someone who is often on the front lines but manages to befriend the right kind of people to keep him from getting burned by it.

And now he got burned.

He got burned badly.

Iris closes her eyes as the tears slip past them and feels not-Barry inhale, reach out to gently touch her shoulder, and she wants to push him away, to scream at him, to break the face that isn't his, you're not Barry, but she's crying, silent, agonized sobs at the thought that he's gone.

Not-Barry captures her in a gentle hug and she fists his shirt, breathing raggedly against his shoulder, feeling the way he's warm and vivid and alive, and he's not Barry but he smells like Barry, he feels like Barry, and he has that same Barry lack of presumption that makes it easy to stand in a room silently with him.

He doesn't capture a spotlight, but he captures her. He's the reason she stays up late into the night, his words spinning worlds he can scarcely imagine, utterly beyond her comprehension. She'll wake him sometimes and he'll sleepily explain it in increasingly simpler terms until at last he's monosyllabic, interspersing explanations with kisses while she presses him to simplify, Barry.

At last he says, The universe is beautiful. It's full of magic. We don't know what forms it takes. We have suspicions. We can quantify them with experiments. We can look at the stars and see our future. Our purpose. Kissing her, he adds softly, The universe is beautiful, but it's nowhere near as beautiful as you are, Iris West.

When not-Barry says, "I'm sorry," she hears it in his voice. She can almost feel the way he would rub her back in long, vertical strokes. He's brilliant but unsteady, perpetually clumsy, a person who operates best in the intangible, yet he knows how to hold her, how to make her feel safe.

And somehow this Barry does, too.

She wants to kiss him, to believe it is her Barry, but the thought of her Barry makes her heart ache so hard she feels like she's going to sob until she bleeds. She can't lose him. She can't lose him.

It takes her – a while, too long – to finally release not-Barry. He ducks his head, blushing, looking apologetic, and she frames his face with her hands, running her thumbs along his cheekbones, feeling his jawline.

"You're like them – like Zoom." Her fingers tense, like she could keep him there, except – "You're a meta-human."

"Yes."

Iris thinks, Break his neck before he breaks yours.

She has to remind herself that she's a cop and that isn't how justice works. Justice is asking first. Justice is confirmation.

So she just holds him there and he looks at her like he would let her, like she holds his future, and she can't look away from him.

"It's a long story," he tells her softly, and she wants to hurt him, to yell at him, anything to make him stop, to make him be not-Barry, but she lowers her hands instead, resting them on his shoulders.

"Why do you look like him?" she asks, looking at him, demanding answers.

He shakes his head softly, looking like he's fighting a war without saying a word. At last, he speaks, cautious, choosing his words very carefully. "Because I – am him. My name is Barry Allen. And I'm from another universe."

Iris' first impulse is to say bullshit, but she's holding living proof in her arms that something impossible is happening.

Nothing is actually impossible. (Barry loves telling her that, loves catching her with a cup of coffee and a kiss, sitting down at the table across from her and already scribbling on his tablet, trying to illustrate his point while she just watches him with fond eyes, soft eyes.) Some things are just more probable than others. Some things are very, very, very improbable, but nothing is impossible. (A sly grin, looking at her with shining eyes because he loves a point, it's like the culmination of who he is to tell her the scientific endgame.)

If we live in a finite universe, then not every possibility will play out. There isn't enough time or space. (Turning the tablet to face her, he clicks and a circle appears in the center of the screen.) This is our universe. Everything that is and ever shall be happens in this sphere. (Fingers dancing, he continues.) Every event that occurs in our sphere is unique. You will never repeat today exactly. Unless – (Another circle appears.) the universe is larger than we think. Much larger. Infinite.

You're doing that thing again. (Light, teasing, reaching out to squeeze his hand.) Where you're not speaking English.

(Blush, dazzled grin, like he can't quite believe it himself.) Iris, if there are an infinite number of universes, every possibility plays out. If you shuffle a deck of cards an infinite number of times, you will play out every possible pattern. (There are dozens of dots on the screen, now, all resembling the first one.) It's called the multiverse. It's the idea that our universe is one of many – perhaps an infinite number, perhaps a finite number – and the possibility that if we could understand the closed nature of our universe, we could break free and explore other universes.

(He takes a triumphant sip of her coffee and sits back, laughing when she just cocks her head at him.) Barry. I have enough trouble understanding this universe. Don't tell me there are more.

There could be more of us. (Musing, playful. Tapping her foot lightly under the table.) If there really are an infinite number of universes, then I'm so glad I get to live in this one. I can't imagine it without you, Iris.

(And that's why she loves him, no matter how quirky and enthusiastic and dorky he is. Because he's sincere and he tries so hard to make the impossible reality, to do something more, be something more, take concepts light years ahead of other physicists and try and weave them into practical applications.)

Iris reaches up slowly and brushes the hair away from not-Barry's forehead. His eyelids flutter shut, utterly trusting, and she can't quantify the emotion that swells in her chest.

It's him.

They're like twins, but Iris knows even that distance is too great: it's him. Somewhere beneath the familiar sweep of soft hair is the nerd she loves, the quiet reporter who tries to galvanize people. Change the world. Unlock secrets that could save, better, and extend lives.

He isn't the same person – and she can feel it, how their lives haven't entangled, how he doesn't quite fit. Were they to share the same bed, Iris knows without proving, he wouldn't hold her like her Barry does. But he would breathe like him and let her hold his face in her hands without protesting, and she's starting to acclimate to the idea, feeling less like she's going to pass out and more like she's looking at someone her Barry would have died to see.

The 'impossible.'

He opens his eyes and looks at her and that sea-green gaze is hers, that gentlest of frowns is hers, that slow, bracing inhale is hers.

It's him.

"How did you get here?" she asks.

Barry blinks slowly, like he's trying to resurface from a dream, and she puts a hand on his arm unconsciously, watching emotion sweep over his face as he ducks his head, looking on the verge of tears.

"Zoom took someone from my world," he rasps. "I had to follow him. He took me here." Then, looking at her, he adds, "Iris, I'm so sorry, I'm—this was a mistake. I have to go."

She catches his sleeve as he turns, holds it as tightly as she can, and there's an energy under his skin like a thunderstorm, low, crackling, waiting.

"Don't go."

Two words still him, and she can't erase her awareness of that pulsing current, the way it underlies his skin, makes his hand fractionally warmer when she reaches down to clasp it.

"Don't go, Barry," she echoes softly, squeezing his hand, and she doesn't know how to feel around him, whether affection or outrage is more appropriate, because there's a part of her that just wants to take him and kiss him until she finds her Barry.

But no one else can ever be her Barry. Only one person gets that title.

Only one.

"Iris."

It's one word, and the way he says it – devastated, torn – is what makes her lean up to kiss him again, and she thinks, Push me away. Make this easier.

Instead he kisses her back and it's everything, it's the way he kisses her when they're alone together beneath the sheets, it's the way he kisses her on the bridge on a moonlit stroll, it's the way he kisses her when they have time and he wants to savor it and she does, too.

He kisses her like he loves her and she can't deny that some part of her loves him, too. She holds onto his lapels, holds onto him, onto what he means, onto the hope he represents for her Barry. She lets him kiss her until she has to turn away to breathe, overwhelmed, head spinning, knowing that she shouldn't be here, that she should wake up soon, it'll hurt less if she wakes up soon, if she can turn to Barry and tell him to stop ranting about infinities, it gives her paradoxical dreams, except –

She traces her hands along his side and he's tangible, more solid than she remembers, and that's when she realizes that this is real.

"How do we get him back?" she asks him, wondering if he has answers, if being from another universe makes him smarter in some ways.

He looks her in the eye and tells her seriously, "We take down Zoom."

We shatter the sun.

Zoom isn't the sun, but he's impossible to take down.

Nothing – and I mean nothing – is impossible.

(Arms wrapped around his shoulders, rocking lightly against him, peering over his ruffled hair at his half-finished paper.) What about cookies in bed?

(A tiny smile, a break to look at her, kiss her.) That is not happening.

Iris looks at him, feels the strength under his skin. Sees the conviction in his gaze. And knows he would go through hell and back to come home to her.

And for the first time, she thinks, I'm not his, either.

She has too much at stake to lose – her whole world, her life, Barry's life – but she wonders what this Barry has to lose.

Whether he has an Iris waiting desperately for him to come home.

"You said you were a meta-human," Iris begins slowly. "Explain."

There's an almost-amused smile on his face as he says simply, "I'm fast." Then, clarifying, he adds, "I'm not Zoom, but I'm like him. On my world, I'm The Flash."

Iris thinks about how many hours, days Barry has dedicated to studying their Flash, like he can somehow unlock everything if he just looks a little more closely. She wonders what he would think if he knew if somewhere else, he was the hero he always talked about being.

And she thinks how much it would hurt him to know that he really was meant to be something greater, destined for a higher calling, to save people.

It would destroy him.

"There was a particle accelerator explosion back on my Earth," Barry continues. "It released a lot of energy into Central City, and some of that energy seeded a storm cloud, which generated a lightning bolt, which struck me. I was in a coma for nine months, but when I woke up – Iris, I was fast."

There's a twinkling in his eyes and Iris wonders what her alternative self must be like. Wonders how it felt to work alongside Barry knowing that he was The Flash. Not just the junior reporter struggling to find a foothold, but a superhero.

"God." She's shaking her head and walking away from him because she needs space, and it helps that he's a hero, someone Barry could never be.

Someone Barry has always been.

She's always seen it, always known Barry was better than the bullies made him out to be, smarter, sweeter, and so much better. Likable, clever, beautiful, charming. Endearing where he lacked suaveness. Effortlessly funny. He was quiet, contained, and sometimes desperately yearning for something he couldn't have, but he was also the reason Iris loved waking up early in the morning just to catch a moment of him asleep.

Iris turns and sees not-Barry, knowing fully well how much her Barry aspires to be the man standing in front of her, solid, strong, dazed but on his own feet, someone capable of extraordinary things.

"Show me," she tells him.

He takes a breath.

She catches a flash of lightning, sees it fading in the air between them, and then he's back with a fresh cup of coffee, still radiating steam.

He hands it to her and she takes it with numb fingers, trying to wrap her head around it all.

She takes a sip and arches an eyebrow. "You know my coffee order?"

"We're – I'm – friends with you – her – back on my world. We're close."

Friends.

Iris doesn't miss the inflection as she sets down her coffee. Doesn't miss the craving in his features as he watches her, careful in every way, not wanting to offend or scare, only wanting to make contact, to show her who he is without scaring her. And she knows he can see her. She can see his Iris in her, how they share mannerisms and looks and a core being, and her heart aches.

"So we're – you're not dating her," Iris clarifies, struggling to conceptualize it. It's hard to imagine her life without Barry. It's already hard enough to live for a week. Indefinitely? It rings hollow, cold.

That's how not-Barry looks. Hollow. Cold. "We're not," he confirms. "Zoom – kidnapped my girlfriend. Her name is Patty."

"I'm sorry." It rolls off her tongue and Iris wants to ask, Why did you kiss me if you're dating someone else? But she kissed him first and she just doesn't want an answer. She can't bear it to hear it from him. She needs to preserve something of normalcy.

"Me, too," Barry admits.

She straightens her shoulders, pushes her emotions down, and says firmly, "We're going to find them."

Barry nods. "We're going to find them," he echoes.

Iris holds out a hand and Barry clasps it with only the slightest frown, confusion clear.

"We haven't actually been properly introduced," she explains.

He squeezes her hand and it's so gentle, everything about him is the Barry she knows under a different mask, and says, "Hi, Iris. I'm Barry Allen."

She looks him at him and sees another world, another life, another them, wonders what will happen to him, to this Barry, and she wants to protect him, too. Because he is hers. Some core of him belongs to her Barry, they share it, they are it, embodying a goodness in her life she couldn't earn. Only graciously accept, grateful to have it in her life, to have this wonderful, extraordinary person named Barry in her world.

So she meets his gaze directly, sees the purpose there, we're going to get them back, and she feels his confidence wash over her.

Everything is going to be okay.

"Hi, Barry," she says softly, "I'm Iris West-Allen."

When she releases his hand, there's a spark.

So in your infinite universes, would we ever end up together again? (She sits on the couch with her legs across his lap, watching him smile as he sets the laptop down and looks at her, needing to convey the seriousness of his next declaration.)

(Barry looks at her with breathtaking specificity, like she deserves his fullest attention, his utmost interest, and he speaks it with absolute conviction.) Of course we would.

Iris looks at not-Barry as they step back and thinks, I hope he was right.