Remus knows that he is asleep on the Hogwarts Express with his face smashed uncomfortably against the window. He knows that he is in his thirties and greying and feeling ridiculous in second-hand wizard robes after a decade of wearing jeans and jumpers. He knows that James and Peter and Lily and Sirius are sitting around him having a nice time, and that in an hour or two they'll be back for another year at the place that was so effortlessly, obviously home.
James swipes a hand through his belligerent hair and grins. "Watch this, Moony." With a flourish of his wand he sends a few Every Flavor Beans soaring from their box to rain down onto Lily's head.
Before the beans hit the floor, Lily is on her feet with her wand fixed between James' eyes. "Don't go looking for trouble, James-"
"I don't go looking for trouble." James sounds irritated. "Trouble usually finds me."
Remus, Peter, and Sirius, who know this to be the hugest lie of the century, laugh from their stomachs. He hears a high-pitched whistling sound of unknown origin.
"Hey, what's that noise?" Remus asks.
"I've read it's the only entirely non-Muggle settlement in Britain," Lily answers.
"Yeah, they've got everything..." Peter adds. His eyes are bright, his voice is unhurried and good-natured. "Pepper Imps- they make you smoke at the mouth- and great fat Chocoballs full of strawberry mousse and clotted cream, and really excellent sugar quills, which you can suck in class and just look like you're thinking what to write next-"
Sirius is lounging against Remus' side with an arm thrown casually around him. He is young and beautiful and roguish in Remus' general direction. He grins wolfishly. "Yeah, but I've already murdered a whole bunch of people in the middle of a crowded street." He winks. "What do ya think of that, Moony?"
Remus screams it at the top of his lungs, lungs that aren't his own, and the words exist around him, thick and viscous:
"Get out of here!"
No no no. He runs away. Everything turns pleasantly fuzzy and dark for a long time.
"I'm going to go and ask the driver what's going on," says Lily. Lily? No...
Shuffling feet, the sound of bodies running into each other, pained noises. Slowly he wrenches himself to consciousness and shrugs off the vestiges of dream-logic. But it is still dark.
He is on the Hogwarts Express. It is 1993, he is thirty-four and greying and he is not going home. But why is it dark?
The letter from Dumbledore. The understanding and the sympathy and the warning about the extra precautions that have to be taken this year. Extra precautions, the guards. The guards. Ah.
First things first. The children.
"Quiet!" He fumbles for his wand and produces some light. "Stay where you are." He can't take them on, nor would it be wise to do so. But perhaps he can keep them from going into the compartment and scaring the children. Which is all it is, he thinks bitterly. Scaring children. As if this train, on its way to Hogwarts- Hogwarts, for Merlin's sake -could at this moment be holding...
Time splits itself into splinters. He has only a moment to remember that it's been well over ten years since he last saw a dementor in person, even longer since he has had to cast a Patronus. He has only a second to wonder whether or not he can do it, and half a second to remember with a jolt the form it took. The door slides open and he has a tiny splinter-second left in which to be afraid.
Remus' breath is stabbed in his throat. A clever one, he thinks. Clever, and cruel- revealing its horrible, corpse-like hand, only long enough to shock all hope of defense out of the occupants of the compartment. He freezes. He knows what comes next, but he cannot do anything to stop it from happening. It inhales all the warmth from their bodies, and the deep, deep cold takes over...
Icy fog rolls in over his eyes and fills his ears. He knows what happens now...The part of him that can still think wonders distantly what it will use. So much to choose from. Too far gone, he invites it to take its pick.
A sleepy hum. "God, I love you so fucking much..."
Please, no...
His voice is muffled by the pillow. "Soooorry, it's too early for me to be such a girl...Look what you've done, you bastard..."
This one is clever, he thinks coldly, and from very far away. So much bad to choose from, and it takes the good and throws it back in his face...
"But really, though.Just...aaagh...I do. So much."
It's been so long since he's heard that voice...So long...
A heavy thud of a small body hitting the floor. The fog vanishes, the voice is gone for good. Remus goes into fight mode: don't think, just act. Anger grows hands and twists his insides; how dare it show him that, how dare it use that against him and then go after these children, these innocent children-
"None of us is hiding Sirius Black under our cloaks. Go."
Remus yanks his wand out of his pocket and stares unblinkingly into the dark abyss of the dementor's hooded face. For a moment he is boiling over with frantic, reckless rage, and it is wonderful, he is fighting again, he has an enemy, he has a point. Then he is having a staring contest with an eyeless creature and feeling incredibly stupid. Only one option. He says the words without quite meaning them, but this dementor in addition to being clever is weak, and the frail wisp of silver sends it away.
The children are pale in the light cupped in his hand with their eyes fixed, unblinking, on the floor. It takes a moment for Remus to register what it is that they are staring at: a heap of spasming limbs on the compartment floor. The flames in his palm scatter bluish shadows over the terrified faces of the students as they crowd around their classmate.
"I think he's having a fit-"
"Someone wake him up!"
"Oh, I wish they'd turn on the lights!"
The words have not left the mouth of a particularly frightened looking boy when the lanterns sputter back to life and the train begins to move underneath them. Remus quickly extinguishes the flames and pushes past a head of ginger hair to the boy on the floor. Time breaks into mad little splinters again, and for the length of exactly one time-splinter he wonders if he is still asleep. Of course he remembers what his best friend looked like, but. 'But', his brain stutters incompetently as a bushy haired girl lightly slaps Harry's cheek on James' face.
"Harry! Harry! Are you all right?"
Harry. A goofy sort of grin yanks at the corner of Remus' mouth. They'd all said that Harry looked just like his dad, graciously ignoring the fact that all babies look the same. Now Remus wonders, almost sadly, if the boy had gotten anything from Lily at all.
"W-what?" Harry opens his eyes.
Oh. That's right.
"Are you okay?" asks the owner of the ginger hair.
"Yeah...What happened? Where's that- that thing? Who screamed?"
Remus' brain has a habit of attempting to tackle far too many thoughts at once. In this particular moment, he notes Harry's response, knowing what it means: of course he alone of the children is impacted so severely, of course the dementor found horrors in his memories that would floor any thirteen-year-old. Who screamed? Oh God. Could-? He observes the unnatural pallor of the boy's face and the sweat accumulating under his glasses, and is run over with a hysterical urge to hug him, protect him. Simultaneously he sees Harry's eyes skate over him in the search for the fled shadow, and he figures something else out. The thought makes him sick; he wants to grab the boy by the shoulders and yell Do you remember me? Do you have any idea who I am? Do you know that after you were born I was the third person to hold you? Even before your father, because he'd passed out, but the Healer said it was alright, that happens all the time?
Then this particular time-splinter is spent and he is a responsible adult. First things first. He retrieves the chocolate from his pocket- lucky that the trolley wares have always been so overpriced- and snaps it into pieces. The unexpected sound makes the children jump.
"Here. Eat it. It'll help." He makes sure that Harry gets a large portion; his colour still hasn't returned.
"What was that thing?"
"A dementor. One of the dementors of Azkaban." The students' eyes are still roughly the size of tennis balls, as if...well, as if a ragged, comatose stranger had just leapt up, saved them from certain doom, and then distributed chocolate.
"Eat. It'll help. I need to speak to the driver, excuse me..."
He eases out of the compartment, makes his way toward the front of the train, and the familiar feeling of what-have-I-gotten-myself-into welcomes him like an old friend.
Everything in bold belongs to J.K. Rowling. And everything not in bold.