A.N.: The first part of this follows my earlier fic Tadashi is Dead. Not strictly necessary, but it'll make more sense.

The days after he was found are fuzzy.

Concussion, says the database in the back of his brain. And that makes sense, because there's a burned lump on his forehead that throbs when he touches it. It's getting better, though, and he hopes it'll take the headaches with it as it heals.

But concussion means dizziness, means headaches, but more importantly means his short term memory didn't make it over to long term. He knows that Buddy and Roger are the ones who found him, and they're still smug as anything over it, but he only knows that because they told him. Buddy says they thought he was drunk, and Roger backs him up on it. Dizzy and confused with slurred words and a hangover-reaction to light. Roger says it must've been one heck of a party.

It must've been, because he can't remember it. He can't remember anything yet.

Blackout, says the database in the back of his brain. But that doesn't make sense. This isn't a hangover, the symptoms don't work.

And he wouldn't have been burned at a party.

Mostly first degree. Partially second degree. Very small spots of third degree. The database in his head tells him how to treat them, even with the throbbing concussion, and he remembers spending an hour laying near-naked in the water of a drainage ditch as Buddy and Roger made fun of him, until the burns were cool. They still hurt. But the damage won't go deeper.

He remembers very little of those first few days, mostly Buddy and Roger's teasing, and the cold air of the homeless camp. They call him the kid, since he can't remember his name. There's a static in his head that keeps him from minding too much.

Then the headaches start to fade, and the static clears, and he can remember things more than an hour ago. And he starts to wonder.

And can't remember.

Where did you find me, he asks. The old service tunnels for the underground trains. But where? They don't know. They were lost. They were just as drunk as him! Do you remember anything about it? Nope, just tunnels. Do you remember when? Again, no.

Alcohol intoxication, says the database. But he doesn't say that.

He spends a lot of time thinking, trying to remember. Buddy finds some cardboard, makes a sign, leaves him with his burned face and slow smile on a street corner for a day, and then buys cheap Chinese takeout. It's not very good, he thinks faintly, but it leaves him full for a few hours and that at least is welcome.

They leave him to his thoughts overnight; the headaches won't let him sleep. His head is a mess, but a sort of structured one. Like a room filled with shelves, their contents mapped out by some logical scheme, but after an earthquake comes along and knocks everything off. The concussion knocked everything off the shelves, but it's all close to where it should be.

He wonders if he manages to put it all back together, he'll find other things buried somewhere.

Like his name.

Like his past. Like his family, if he has one. How old he is. How he got these burns. What good Chinese food tastes like.

All sorts of things he'd like to know.

Amnesia, says the mess on the floor of his head.

He starts picking it all back up, examining it, sorting it. He thinks all day when Buddy leaves him on the corner with his sign again, and all night after a dinner of almost-expired rolls and soda when they camp under an overpass. He thinks as they walk, when a heavy rain floods their usual camp. He thinks on another corner, and next to a road, and in the lobby of an overcrowded shelter as Buddy tries to get them beds.

After a few days of thinking, the headaches finally let him pass out, and when he wakes up rested he realizes he's only learned one thing:

He knows a lot.

And he doesn't know how he's learned it.

He finally reads the sign Buddy gave him. Apparently for the past few days he's been out of work, anything helps. Which, he supposes, is true. Buddy's sign, Wife, Three Kids, please help, is not. Roger's sign, Hungry, is very much so.

Malnutrition, says the much-better-sorted database in the back of his head. He keeps thinking, and ignores his stomach.

They're on the move again, headed towards the entrance to a tunnel that Roger swears is warm at night, when a bar brawl bursts out of a side door and straight into Buddy. The fighting men don't realize they've picked up a bystander until his face is already bleeding.

Minor abrasion, facial lacerations, potential broken nose. Buddy tries to put his fists up but only catches another blow, and it knocks him down – fall. He tries to catch himself, but falls wrong, and lands hard on his elbow – potential broken arm. Buddy collapses with a cry of pain, and his head hits the concrete – potential concussion. That draws the bartender out, who chases off the fighters with threats of police and wives and parole officers, and offers Buddy the use of a first aid kit. Roger goes ahead to make sure they have a spot in the tunnel.

The bartender might have a first aid kit, but he doesn't know how to use it. Buddy can't think of anything but to drink the pain away.

The task falls to him. He checks the arm – No break, minor sprain – and wraps it. He checks the nose – Broken, not shattered – and sets it with stiff tape and blunted toothpick halves. He washes the cuts – deep, but not near an artery – and closes them with medical tape before bandaging them over.

By the time he's done, Buddy's calling him Doc.

They head down to the tunnel, Buddy much less sober than he was. He looks a mess, and acts one, and tells everyone how Doc saved his life. He didn't, but the story is better.

The nickname sticks.

The air is turning to fall, and it's obvious at night. They stick to the tunnels at night, when they can – it keeps them out of the wind. He catches something that he can't quite identify – not the flu, there's no fever, not a cold, the cough is too deep. Pneumonia isn't something he can treat on his own, and he hopes desperately it's not that.

But he's fading in and out of consciousness, tired and sore as only sickness can make him. He curls up in a tunnel, far from Buddy and Roger. Maybe he won't infect anyone else this way.

He's near asleep when something prods at him. He pries his eyes open to see a black mesh tendril snaking past him. It's not a solid thing; it's hexagons of some kind of... tiny robot. Oh. Okay. It doesn't strike him as odd, and he's too tired to wonder why. He closes his eyes again, and lets it pass him by.

Another one prods him, and other, and eventually they wrap around him like a birds nest and set him aside. He watches them pass through half-lidded eyes. A man in a white and red mask moves with the swarm, and vanishes again. A pair of robot arms that he recognizes as being used for manufacturing are dragged after, then hundreds and hundreds of empty trash cans.

He falls asleep before they finish passing, and when he wakes again they are gone.

He feels better. It takes him a while to find Buddy and Roger again. They thought the swarm had got him. But he isn't afraid of the swarm.

He almost wonders why.

His head is better now, and he tries to find a job. But it's hard, when Doc is the only name you can put on an application. No contact information, no history, no green card, no social.

No job.

He spends his time in the alleys, in the tunnels, and his nickname starts to become his job. People will share food if he'll set broken fingers, even if all he has is sticks and scotch tape. He saves up enough from a corner, and buys a first aid kit and a big bottle of hand sanitizer.

Food for bandages. A place by the fire for a tentative diagnosis. A pair of old gloves after the Heimlich maneuver saves a man's life. Buddy and Roger are always around, and they spread the word.

Hurt? Doc can help. Burned? Doc'll make it hurt less. Cuts, bruises, mystery cough. Doc knows. Doc can help. Go see Doc.

He's helping people, and he's happy. He finds a backpack, and keeps his supplies on hand for when folks walk up on street corners to ask if he's Doc.

The back of his brain tells him he could do more, that he did do more. There's so much he can't cure that he could. That back at some point when he wasn't hungry and he didn't have scars, he was working on something to change everything.

He can't remember anything more.

He listens; he has to listen, or he couldn't find people to help. But the gossip is strange lately. Ellis saw the swarm again. Karen says it threw a van into the bay once. The Cooper family saw it eat a junkyard. Paul says it lives on an island. Ivan saw it pull red birds from sea.

There are theories. It's an experiment from Krei Industries. It's a hive mind. It's from space. The man in the mask is controlling it with ESP. It's a devil. It's a bad trip. It escaped from San Fransokyo tech when it burned. It's genetically engineered from ants.

It's dark, it's evil, it's the unholy union of shape and shadow.

He's the only one who's not afraid.

There's a bust at Yama's. Police are everywhere, cars blocking alleyways, and the homeless scatter. No Loitering, No Soliciting, No Panhandling are rules they've all broken, and though cells are warm at night, the police are not gentle. They're not here for them, though, and he stays to watch as they round up the bettors.

They wheel out the robots as evidence, deactivated or torn to shreds. A part of his mind that he hasn't sorted yet perks up at that, and he scans their metal skeletons with a practiced eye.

Magnetic servos in one. A sparking mess of wiring. Plastic and aluminum frame – cheap, no wonder it lost. Ball bearings bleed from an axle. It takes two officers to carry out Yama's latest creation. It's built for brawn over maneuverability, well balanced, low center of gravity to be hard to tip, carbon fiber samurai armor. As heavy as its maker.

He wonders how he knows.

He can't find Buddy and Roger, and he wonders if they were arrested in the bust. Without them, he has to rely on his own knowledge of the city, and he sticks to the tunnels.

The swarm passes, now and again. People stop running from it; they just get out of its way. It doesn't want them. He watches it tear apart a junkyard from a distance, meets the dark eyes of the man in the mask. He feels like the man notices him; though there's no change in the man's behavior, the microbots always edge a little further from his feet no matter where he stands.

He's not the only one to notice. The swarm avoids Doc. The rumor spreads, and now he is welcomed by the sick and the superstitious both.

A weirder rumor, one day: A kid riding a miniature jet. It was red, says Old Bill, as Doc cleans the long scrape on his arm. Thought it was aliens and nearly dove off the bridge.

He wouldn't have given it much further thought. But Bill wasn't the only one to see it.

And he wonders.

He's just finished removing a splint from a healed arm when the commotion starts. This place is a hub for the service tunnels, rounded off with a higher ceiling that makes everything echo, so it takes him a minute to find its source. A family runs to him, their youngest wrapping their arms around his knees. The swarm, the swarm, and it's angry this time. One of them has a scraped knee, and he treats as he listens. The man in the mask has never spoken to any of them, but he is now.

The masked man is angry. And the swarm is part of him.

The swarm avoids Doc, the murmur starts, and people start pulling him closer. A distant rumble echoes from the tunnel the family ran from. It grows into a roar. He finds himself at the head of the crowd. There's a mass of bodies behind him, trickling off into side tunnels and trying to climb to the surface, and he is the shield of the ones who stay. The tunnel is black.

Then the swarm rushes in, washing through the room like a tidal wave. The neat hexagon patterns of the tiny robots have been replaced by sharp triangles that snap into place with electric speed and obvious force, and they fill the room as a cage around the edges. They keep coming, keep spreading, the walls thickening by the meter until the room is claustrophobia-small, and then the white mask appears.

There aren't many people behind him now. They've mostly run; his alleged power over the swarm is no match for the swarm itself, especially not when it's bigger than they've ever seen it. Even he is beginning to be afraid. The swarm shouldn't be angry. But it is.

The man in the red and white mask faces him, and emotion bleeds from the posture even in absence of a face. Angry. Desperate. The man is tense as a rope and shaking. Elevated adrenaline levels. Lack of sleep. Psychologically unstable. There are so many diagnoses that fly through his head and not one is helpful. He takes a careful step forwards towards the man.

And everything explodes.

"Get out!" The roar is everywhere, the voice from the man and the swarm. The tendrils become spikes and fly towards them. The walls collapse like a storm at sea. The whole thing is lunging, seething with inhuman anger. The others scatter. The world echoes with panic, and he takes a step back. "Get out! Damn ghost!"

The swarm lunges at him, an amorphous lump like an oversized fist, and he stumbles backwards and runs.

He makes it to the surface, gasping.

No one comes near him for the rest of the night.

He spends most of the next day alone. The swarm hates Doc is the rumor now, and it's enough to keep people at a distance even in the light of day. Then the news spreads, in the late afternoon. Someone's fighting the swarm. The boy on the red jet. A three eyed monster. A yellow blur, a pink-armored girl, a man in green with knives in his arms. He finds his way to the scene to watch a hole in the sky suck up the world.

Then the swarm collapses. The hole in the sky falls with a crash. The tiny robots scatter like dust. The boy and the red jet – red robot – are nowhere to be seen. And the man in the mask no longer has his mask; he has a face, and it's familiar.

He wonders where he knows him from.

The boy emerges from the hole without the robot, clinging to a white rocket with a frosted window. The others rush over, and there's some uproar about she's alive. He's forced to step back when police and ambulances descend on the scene as thickly as the swarm had.

The heroes disappear. The girl from the white rocket is loaded into an ambulance. The man in the mask is forced into a police car. Their eyes meet.

That man could tell him who he is.

And the car drives away.