When it comes to Speed Force, there is a line that Iris cannot cross.

She sits on the rooftop and waits for it anyway, knowing that the storm is coming soon.

Awareness of the barrier does nothing to curb her fantasies of experiencing Speed Force directly. Powerlessness to change her fate intensifies her hunger, flaming a rebellion against nature. She refuses to concede absolutes to the universe: never is only true until the first time, and always is just the same until the last.

The lightning chose Barry, but it needn't have done so to her exclusion. It could still happen. For Wally, his transformation took place fully two years after Barry's bolt from the blue. Iris' patience endures the test of time for one reason: the alternative – never – is unthinkable. She won't live an ordinary life when the extraordinary is literally at her fingertips. To walk away from a vision so great is unbearable.

She wants to bathe in that lightning, to feel its current course through her, to rush alongside it, its power buoying her. Speed Force is an ocean bridled under Barry's shoulders; when he's near enough, its tide draws her towards him. She may come as close as she dares, infinitesimally so, but she can never touch it, only stand at the edge of the water, aching and euphoric for something more.

It has a name, that humbling invisible Other, that emissary of its great and inconceivable source, a Mercury of modern times. The Flash. She gave the moniker to Barry, inextricably tying the two together, he the hero, Flash the herculean. The lightning-in-Barry's-eyes and under-his-skin are reminders that Barry and The Flash cannot be fully separated any more than a heart can be from its pulse. Call it Speed Force, call it Mercury, call it anything at all: Flash remains the living link to the unliving, beyond-living Speed Force, a Great Presence in a humble world.

Once, when she was younger and drifting and two-thirds of her thirty-nine years, she saw Barry's relationship with The Flash as a drawback. She wanted to love Barry as Barry and not as his namesake. But the lightning loved her, and loved her, and loved her, edging closer as he did, enveloping her in warmth like he did, echoing his emotions so intensely and purely that she could not help but fall in love with it, too. Barry was not just Barry; he was The Flash. Their union was total; to reject one was to ignore the heart of the other.

When Barry was hurting, Flash was there for him; and when she was sick or weary or hurting, too, Flash was there with golden eyes and tender warmth. Expressing her gratitude for them both, she could hug Barry, and it was almost enough, like love behind a closed door. Speed Force and she could press their hands against opposite sides of it, but their contact was always indirect.

Until it wasn't: when lightning skipped from his fingertips to hers; when the energy lifted her effortlessly as he ran; when she could feel the occasional soft, reverberating rumble in his chest as he slept, not snoring but almost purring, a quality their days-old twins found indescribably soothing and she found soothing, too. She felt it in those moments when lightning transformed shiners into fading yellow bruises by nightfall, knitting, healing, always at work. Sometimes she felt it as it leaped beneath her hand, hardwiring a heart rate so fast it is scarcely detectible.

She wanted to feel – just once, for one minute, even one breath – what it was like to know that lightning so deeply. To run freely without fear of crashing, knowing she would survive because Flash was always smarter and faster and ahead of Barry, quietly and unconsciously teaching him things he didn't know he needed to know. (Not least of which were tricks of the trade like how to not die from a crash at six hundred miles per hour.) Speed Force loved her; it would not let her come to harm while she was with it.

Her thirty-sixth birthday approaches, and Speed Force has never given her more than an insatiable thirst for more, but she doesn't resent them. It is a them – Barry and Flash both, indistinguishable at times as they stand helping and healing where they can, respectively – and it would hurt more if it was anyone else. With Barry, she gets to experience Speed Force as an adoration, its energy focused towards her. She likes to believe it would be the same even if it had never connected with Barry, but she doesn't know. Maybe Flash only loves her because of Barry. But it loves her in its own way, a call like an ocean, an awesome example of real and otherworldly, the stardust of the universe, the Before to the question when did you come to be?

She knows and loves Flash, knows and loves Speed Force through it. Flash is the intermediary between the two: the truly unknowable Speed Force, and the utterly worldly, human presence of Barry. It conveys a sense of scale, of something far beyond her comprehension, escaping definition.

Speed Force isn't something she can truly know secondhand. And, she knows, Flash is Barry's and Barry's alone.

Wally's experience with Speed Force isn't like Barry's vast, celestial sea: Wally's is joyful, intense, and shallow, like whitewater rapids. Next to Flash, Kid Flash lives up to his namesake, taking an almost fiendish delight in clocking faster times. Iris can tell them apart by their lightning alone, how Barry's deep bond with Flash is titanic and golden while Wally's fierce love of his own dynamic Speed is all silver and red. It shows in subtler ways, too; Barry runs warmer than Wally, and Wally's heart rate is impossible for her to detect, it's so quick.

(I never realized yours was slow, she teases Barry, lying next to him, head on his chest.

I didn't, either, Barry replies, an arm around her shoulders, pleasantly unruffled.)

Because they have empirical evidence from not one but two sources: Wally and his lifelong, his forever, Jesse Quick. She's just as fast as he is – they've been locked in a tie since they first hit the ground running, his rapids rushing across her avalanche – and seems to take tremendous pleasure tackling his bronco Speed. Sometimes quite literally, an exercise which is indubitably spectacular to watch in slow-mo but too fast for Iris to watch in real time. Jesse keeps Wally grounded, and Wally keeps Jesse hunting for the starry nights, and the two of them are speedsters in love in a way that makes Iris' heart ache.

She's happy for them and their mutual successes, even though she already foresees inevitable challenges in Barry's life and her own. For starters, they never decided if aging would be a problem for Barry – too fast or too slow? – but Iris has the chilling suspicion that one way or another, their longevities no longer share the same brackets. There are days – whole weeks, even – where Barry disappears to a place she cannot follow, communing with the Speed Force directly, in Limbo. There are little challenges, too, moments when Barry moves too fast for her to see, when her own actions must seem to drag out for minutes or hours in his eyes. Sharing a life with a speedster is an adjustment for anyone but another speedster.

Even then, she sees the push and pull between Wally and Jesse, Barry and Wally, Jesse and Barry. She sees how their interactions are at times strained because of Speed-deprivation, be it metahuman-induced. Speed diffusion – the escape of that unkeepable substance into the world, warmth into a cold, cold multiverse – is natural for all of them, but Barry alone seems immune to the chilling effect. Flash's connection brings Barry a rich and seemingly (indeed, probably) limitless supply of Speed; Kid and Quick are bound to the multiverse, failing to enter Limbo on their own.

Only with Barry's help can they recharge, falling back on Flash for help, and Iris wonders what her relationship with Flash would become if she, too, could run. Would her Speed be fast and furious, like Wally and Jesse's, or slow and deep, like Barry's? Would she burn out as Eliza Harmon did or die an excruciating death like Zoom? Would she master her Speed at all or find herself at its mercy, as Eobard Thawne too often found himself compelled by Reverse?

(I feel sorry for him, Barry admits unexpectedly one evening. There are times when it's extremely difficult for me to find my way back and I have you. I don't know who I'd be without you, Iris.

Not like him, Iris insists, leaning against his side on the couch.)

But does she know? Can she?

What does Speed Force sound like? Taste like? Smell like, even? Is it a storm or a sea, electrical current or wave, humbling or humble?

"Something on your mind?" Barry-as-The-Flash asks.

She turns to face him and he's standing there on the edge of the roof. "You've gotten better at stealthy approaches," Iris muses, walking towards him.

"Never," Barry replies with a smile. "You just didn't notice. Which is why I asked." He saunters closer, all lightning and come-with-me, and I-want-to, I-want-to, I-want-to. When he wraps his arms around her, it's almost too sweet to bear, her eyes tearing up as she presses her cheek against his chest. She can feel that th-th-th-th-th-thump heartbeat, achingly close.

Let me be with you, she requests. Please.

"Iris?" Barry asks softly, and the teasing has dropped from his voice, his voice, and she knows without looking that his eyes are green again, too. The Flash is still there, though, with every beat of his heart, with every ounce of warmth his touch infuses. He presses his palms gently against her back. "Are you okay?"

I smell the storm on you, she doesn't say, holding onto him. I taste it on your skin, the salt of ocean waves. I can hear the quiet thunder in your voice and in your dreams at night, when you don't even know it's there. Or maybe you do, and it says something different to you, and I want to hear that conversation.

I want to know what Speed Force has to say, and what it is, and why it didn't choose me.

She doesn't need to know what it looks like because it's there, right there. Close enough to almost touch, in the lightning in his eyes, in the warmth of his smile.

But there is one question she cannot answer.

What does Speed Force feel like?

Years ago, Barry gave her a simple answer: It's an energy system. Which explained nothing because, as he later described, everything was an energy system: people were energy systems, as were oceans, and campfires, and atmospheres, and songs. But it was a good answer, too, because it left nothing out. It said, Speed Force is a song, an atmosphere, a campfire, an ocean. It's a universe, a creature, and another dimension. It's a state of being, a time in space, an infinity and a great void.

"Can I show you something?" Barry asks, rubbing her back slowly, up-and-down, up-and-down. "I want to introduce you to someone."

Iris doesn't dare believe, just nods her head even when a painfully optimistic corner of her brain surges with dizzying readiness to the forefront of her thoughts. Barry pulls back slightly and lifts her bridle-style, effortless as always. She hooks her arms around his neck and closes her eyes. Then he takes off.

She feels the shift immediately, the weightlessness that is not powerlessness overtaking them. They don't stop, but they do slow down, and she dares to open her eyes.

They're still moving fast, but the world around them has come to a halt, and all she see in all directions is a sea of stars. There is a soft golden glow reflected onto their skin, illuminating them both like errant constellations. Barry keeps a firm grip on her, refusing to surrender her to that energy which would happily, immediately take her into its midst. Iris doesn't fear the endless space around her, empty in all directions, fuller than anything she's ever known, as if the ninety-six percent of recognizable matter that didn't exist elsewhere was fully present here, a profound ether, a gorgeous void.

She reaches out and there is something there, something indescribably sweet, haltingly real. She isn't sure if it's a blessing or a curse to know it; it is the realest substance she has ever encountered, Everything she has ever known compressed into a single indefinable moment. It's eternity, too, energy that does not age or dim or die.

It's like her first and last breaths, and she is mesmerized by it, mesmerized that this is the place to which Barry runs, and when the stars vanish, the Speed Force does not, conjuring instead a more familiar realm and Barry slowly, slowly comes to a halt.

He sets her down gently but keeps a vigilante hand on her arm, like he's afraid she'll fall forever if he let go, and maybe she would, and maybe she should be more afraid of the prospect, but how could she be?

The Ghost hovers before her, exactly as real as she always knew it was.

"Flash," she says. She reaches out a hand to touch and thinks it'll disappear, that it'll fade before her fingers make contact, but it stays, and for a moment, she is lightning.

She feels the love and warmth and burning rage, the fear and submission and uncertainty, the chaos and collaboration and wild insistence on life. She feels the urge to run like the urge to sing or dance or kiss, a tender, overwhelming sense of pride and awe overcoming her. She senses the hand still on her arm, a gentle grounding force, but feels Flash's airy unconcern for time and space and all that is, because it is simply surrounded by its own existence, and all else is temporary and harmless.

But this, this is forever, Eternal, Always, stronger than imagination could perceive, more alive than her human senses could hope to perceive, intimately, utterly engaged with her. She does not run, but she does not need to, absorbing Flash's own experiences, remembered joyous-trampling-gallops through big empty fields, Icarusian flights over vast mythical waters, wonder-infused jaunts through sleeping cities. She feels the pain and joy of the shared existence Flash has with different Barrys, intersecting in time if not space, the physical toll and the mental confidence, unbreakable, unbreakable, unstoppable, Iris.

She savors the power and overflowing love of Flash's presence, savors it until the very moment it is well and truly gone, evaporated into the empty wind, the indefinable cosmos. Barry is slow and weary but still strong enough to lift her into his arms and take off.

When they come to a halt in an open field, there are tears on Iris' face, an irrepressible laugh bubbling out of her chest. "Oh my God, Barry," is all she can say, pacing and shaking her head, wonder and disbelief and joy crowding out all other thoughts.

The most extraordinary sense is that Flash is still there, right there, looking at her through Barry's tired fond eyes (and she'll learn later that jaunts into Limbo tend to be exhaustive on him, requiring a total surrender to Flash's intuition and subsequent utter drain on his own resources). She can see it and feel it and know it, knows as surely as her own name that it chose her, too, and it didn't give her lightning because it never needed to.

You don't need it to be with me, Flash says without speaking. I'm right here.

She walks up to him and he hugs her, their embrace lasting longer than Barry's trembling legs seem fit to hold out for, but he doesn't complain, and she can feel the steady thrum-thrum-thrum of Flash keeping him up, a crutch when he needs it, a companion in all times.

"I love you," Barry says, and Iris knows it's a mutual feeling, that the lightning is just as fond as it skates over her fingertips, all blue-blushing light, and it's the last bit of energy he has to give and he gives it to her so she might be with them, together, again.

She didn't know that four weeks later, Barry's life would be taken from her in a crisis. How could she have?

But when Flash returns to her – a ghostly presence she immediately recognizes, immediately knows – she feels the same sweeping ease, the breathtaking relief that she felt the first time she met it in the Speed Force, at home. Because if Flash – any version, as it turns out; every Barry has their own – is there, then her Barry might be, too.

Iris West-Allen is patient above all else.

And speedster though she may not be, she knows the Speed Force will always be there for her. It's not just a part of her life; it's her friend. And it always has, and always is, and always shall be.