It's a disagreement between the Speed Force within him and his human side.
All Barry knows is that he burns hot, and sees things, and wishes it would end sooner.
Caitlin tells him to stay off the streets, to rest, but there is a restless animal inside him worrying him with its teeth, insisting one word over and over. Run.
He turns off the mic and patrols.
He'd leave the suit behind, too, but he can't risk it. He's fast, but if he slowed down for even a moment and someone saw him, Game Over. Besides, he likes the suit. It keeps him cool, or warm, depending on his needs. It responds. It flexes with his breath and holds him together when nature conspires against him. It is his life support and his last resort, his trusted sidekick in every fight. He needs it. He doesn't know when he stopped wanting and started needing it. He suspects it started when the bad guys brought out the bigger guns. Bring armor to a swordfight.
Before midnight he stops a man attempting to steal a woman's purse. The mugger socks him hard in the jaw. Barry's head snaps back, pain radiating at the point of contact. He doesn't miss the astonished look on his assailant's face. Before the mugger can press on, Barry snatches and Flashes his quarry to the police, dropping him gracelessly outside of Singh's door. He doesn't care that he has no explanation to give to ensure the man receives his comeuppance. The rest of the world still needs him.
Burning up or not, he has a duty. A higher obligation. He brings comfort to his city, sitting beside a homeless man and letting him rest his shoulder against Barry's. Barry opens his mouth to speak, but he can make only a thin, indefinite noise. Shutting it, he listens, and loses track of time.
Religion, he once heard, is defined by one's ultimate concern. Barry's has a pulse and a rhythm and craves his kinetic worship. He leaves the homeless man, and doesn't miss how much Speed he leaves behind, like he's bleeding out.
He channels it into other people, arriving at the hospital and asking the staff if he can help at all, and they don't need to ask, How?
They guide, and he takes a seat. He sits at the bedside of an elderly woman and holds her hand, and her wheezing breath settles. In a slow halting voice, she talks about her kids. He thinks about his own, but even as his reality bends he remembers that he doesn't have any. Somewhere, he knows, he is already ancient, and he has twins. Their names are Don and Dawn, he thinks. We call her Dar.
A nine-year-old is absolutely mesmerized by his cowl. Speed-sicknesses aren't contagious, a quiet voice inside him assures as he dips his head so she can run her fingers over the lightning bolts. She asks how old he is and he has to smile. His voice is gone, so he holds up his hands, all ten fingers twice, seven fingers once, and she nods and holds up nine of her own fingers in response. He holds her hands and pours every ounce of healing he can into her, aching to cure that which he can only mitigate.
He visits a lot of kids. They take the most out of him.
He's on fumes by the time he hugs an exhausted intern at the end of the hall, her hands fisted against the back of Barry's suit.
Sometimes his worship is awesome and inspiring, battling giants, but it's the quieter love he extends to those who need him most that compel him. Even when his shoulders slump, and his lightning fades to a burning ember red, he doesn't let go. He lets the intern back off, and she says, "Thank you." He dips his head in acknowledgment.
There's a scuffle in an alley outside and he breaks it up, taking a knife to the gut for his trouble. He rips it out and delivers a knockout punch, feeling the sharp pain in his stomach with astonishing clarity. His world sways dangerously as he gasps and staggers away before anyone can touch him, Flashing home.
Except he doesn't end up at Joe's or even his own apartment; he crashes into a table at Jitters. It knocks the wind out of him, his body slumping to the floor before he can even think to rasp for help. Go home, he orders his twitching legs, unable to stand as the startled night-shifter approaches. Get up.
He blacks out instead.
Consciousness hits him like a sledgehammer; he groans and turns his head and meets a couch cushion. Opening his eyes does little to improve his view. He sees a shadow crouch in front of him and reaches up with a sluggish, aching hand to feel his own face. His breathing shallows when he feels the mask.
"You saved my sister," his companion, he can't be more than twenty, points out. "Last week. The shooting at the bank."
Barry blinks. He opens his mouth and manages only a weak whine. His companion squeezes his shoulder and Barry shuts his eyes. There's a headache pressing menacingly at his forehead, trying to drag him down into incoherence. His companion asks, "Can I call somebody for you?"
Barry shakes his head. He doesn't dare.
His companion squeezes his shoulder and says, "Hang tight, Flash."
Barry hears him get up and tries to follow, but none of his limbs cooperate. He sinks under instead.
When he opens his eyes, his mouth is dry, his throat is sore, and his head is throbbing full force. His buddy isn't in his immediate vicinity. He forces himself to sit up and puts his head in his hands for a moment, regrouping. Idly, he presses the comm, but he can't make a sound, and – being geniuses – they never thought to include a panic button.
Hard way. All right.
He can't say how he gets there, just that he stumbles through the dark, half-blind, and ends up through muscle-memory at his apartment. The stairs are dark, and empty, and cold. It's only once he stands outside the door that he realizes he doesn't have his key.
Or his phone.
He sighs and presses his forehead against the wood, a tiny thunk, and he thinks, C'mon and cannot rally his strength.
Unexpectedly, the door slides open and he pitches forward, catching himself with a hand on the doorframe as Iris makes a startled sound. "Barry?" she says, sliding an arm under his shoulders, supporting a fraction of his weight he wouldn't think possible. "Hey, hey, it's okay." She helps him walk, stiff-legged and sore, over to his bed.
He groans and feels something hot trickling down his side and thinks, The suit hides the blood.
With heartbreaking gentleness, she slides her thumbs underneath the cowl's edges and tugs it off. It's a gesture that should set his heart racing, but he trusts her, and even with all higher functioning turned off, he trusts her.
The top half of the suit follows, and he holds her arms and tries to tell her what matters. Their names are Don and Dawn, he thinks, rubbing frozen thumbs over her forearms. We call her Dar.Don and Dar.
Iris says, "Bar," in that quiet, hurting tone and his stomach twists.
I'm sorry.
His hands slide off her arms.
She cups his face and he leans into it. She's so good, so good, he loves her so much, a love like delirium pushing against the smothering heat. Insisting on existing, if only for her. I want to stay with you.
His stomach hurts where the sharp-deep-ache resides. It's not hot anymore, though, which tells him that it's not bleeding, which is good, except he's already bled-out his Speed, which is bad.
She disappears and he reaches for her. When she comes back, there's a warm cloth in her hand, and oh, oh, that stings. "I know," she apologizes.
Don't apologize, he tells her, sweeping a thumb across her wrist.
She sits on the bed and he wraps an arm around her, holding on, forehead pressed to her hip. I love you, he tells her. I love you.
She settles a hand in his hair and scratches lightly. I love you, too, she doesn't need to say out loud.
Her warmth is like lightning, healing and whole and right there, and he sighs and settles into it, basking.