Before he opens his eyes, Baymax knows what happened.

The equation is simple. Feedback- in this case, aural- is translated into data, which in turn acts as a nearly-human 'sense'. He can't stop himself from thinking a certain way, because it's not really thinking at all.

So when he hears the silence- silence that, minutes ago, was filled with the cacophony of arguing, shouting, and running- he already knows. It's not without dread that he activates his visual receptors.

He sees the girl first. The chemist. She's trembling, hand pressed against his front, looking up at him with an impossible combination of fear and hope and worry. He doesn't need a scan to know that she's hurt, as a brown-red gash along her arm is still dripping onto the floor of the lab-

-where something is shattered beyond repair. Red and black shards litter the ground at Baymax's feet, and if he had any lingering doubts about the last five minutes, they're chased away immediately.

He looks away, but the destruction is everywhere. Rubble is strewn throughout the area, and half-crumbled walls are visible through swirls of dust. The other members of the newly formed team are standing, kneeling, trying their best to tend to one another, but his gaze is drawn to the other end of the room. A small figure is hunched over, both hands splayed against the floor.

A quick scan tells him that Hiro has recently vomited.

The image, more than anything else, sticks with Baymax. It's not thinking, exactly, nor is it feeling, but for an instant, he has... the sensation of how wrong this all is. When last he closed his eyes, Hiro had been furious- scrambling past his friends' arms, screaming as they tried to hold him back.

Now, he's still.

Hiro is never still.

Baymax tries to move forward, to reach him- to help him- but one of the others stands in his way. Fred, if his memories are operating correctly. The usual spark in his eyes is gone, replaced by determination and uncertainty as he holds his arms out wide, keeping Baymax from taking another step.

For the first time, Baymax doesn't know what to do. He tentatively offers to heal their wounds, but only suspicious stares answer. Hiro's friends are staying a distance away, but move as if they're trying to corral him, tracking his every movement.

When Hiro walks through the center of the group, ignoring them all, Baymax is as surprised as the rest. They crowd him, asking if he's okay, the questions piling on top of each other until he finally holds up a hand.

"Baymax." He keeps his eyes firmly on the ground. "We're going home."

He almost inquires about Hiro's physical condition as the boy walks away. Almost. He considers his memories of their interactions together, his knowledge of emotional states, and his deduction of the events here at the lab, and decides not to ask.

[]

They're flying back, and no one has said a word.

Baymax is starting to suspect that Hiro, like his companions, is under the impression that he doesn't know what happened in the lab. He might be clinging to the hope that, somewhere in the exchange of data chips and the building's hectic decimation, Baymax's memory was damaged or incomplete. Perhaps this is why he lies flat, staring straight ahead and not moving in the slightest during the flight.

He can't lie, of course. And Baymax suddenly realizes that his own silence may contribute to the misunderstanding- Hiro might believe that he is compelled to divulge everything he knows. After all, doctors could never withhold information from patients.

But they never ask directly. So Baymax doesn't tell them, and he certainly doesn't tell Hiro. In his mind, at least, Baymax can continue to be what he always has been- uncorrupted and pure, without any knowledge of what he's done. It's a judgment call, and not for the last time, he asks himself if it's the right decision.

They escort the team members to their homes, one by one, and it isn't long before Wasabi has his feet planted firmly on the ground. He asks what Hiro will do next, but the boy responds with a shrug. Just before Baymax takes off again, the man sighs and rubs his forehead, his hand covering his face. "Keep an eye on him," he finally says.

Soaring through the sky, a brilliant sunset on one side and the oncoming night on the other, Baymax wonders who he was referring to.

It feels too soon for the house to appear, but suddenly they're standing in the backyard, then the hall of the café, then the stairs, and then Hiro's bedroom is as dark and quiet as night itself. Everything looks the way it always has- the beds, the posters on the walls, the haphazard scattering of research and clothes- and he takes a second to look through the window. Miles away, on a secluded island, something is radically, fatally different.

It's strange, he considers, that one event can impact so much.

"Uh... Baymax?" He turns to see Hiro, already free of the powersuit, standing in the center of the room and looking up at him. He coughs once in a strained wheeze, and when he speaks, it's slowly, like he's having trouble finding the right words, or working through his thoughts. "You helped my emotional state."

Not a thought. Not a feeling. But it's all terribly, terribly wrong.

Hiro drops his gaze. "I am satisfied with my care," he chokes out, and once again, Baymax doesn't know what to do.

[]

Hiro doesn't activate him much after that.

The first time, not even the whole night has passed. He's sitting up, half-immersed in nightmare, hands grasping at the bedsheets, eyes shut tight, breathing quickly and exhaling in an uneven whine Baymax hasn't heard before. And when he tries to help, when he holds out his arms and tells him it'll be alright, Hiro panics and tries to shove him away, and Baymax looks down and realizes that deactivating the powersuit made visible a smear of dark blood on the white surface of his hand.

Treating shock isn't too complicated. Identifying what could lead to hyperventilation doesn't take long, and it isn't difficult to get him to calm down. Looking at Hiro, though, and seeing him shiver with a wild look in his eyes, Baymax knows that he isn't doing nearly enough. He can't.

Especially since he was the one to...

The idea is troubling. Baymax understands the details of what happened on the island, of course, but the concept of blame makes itself known for the first time, and he can almost feel a physical pain when he considers that he is capable of hurting Hiro in far greater ways than he can help him.

The next time, Baymax can almost pretend that nothing has changed. The room is lit up by warm sunshine, and Hiro is before him, hands jammed in the pockets of his hoodie, asking if he wants to take another flight around the city, just to see the sights. He's still avoiding eye contact, and Baymax guesses that 'pretending nothing has changed' is exactly what the boy intends to do.

It isn't until they're in the air, and he notes the drastically colder temperature, that Baymax realizes weeks have passed.

He doesn't get any answers during the excursion- Hiro's smiling again, and it's so profoundly different than the look he had before that Baymax can't bring himself to ask. But eventually, when they're back in Hiro's room and he's sitting on the edge of his bed, tossing a half-finished robot from hand to hand, he explains.

Honey Lemon was the first to suggest going to the police. No one really knew what to do, and they certainly weren't going to implicate themselves, but she came up with the idea of an anonymous tip. After all, it was just a disappearance back then. Not a death. So when the island was searched, and the body was found, nothing could be traced back to Baymax.

Hiro shut down the team anyway.

He doesn't say why. When Baymax asks, he just blinks, and the reason becomes clear. Traveling with that group, wearing those powersuits, trying to do good- it would all be a painful, constant reminder of the very memories Hiro is desperately trying to forget. And when Hiro tells him he hasn't spent time at the school at all, not even to visit his friends, Baymax makes the connection: the most famous and well-loved professor is gone. He can't go back.

The conversation goes long into the night, and Hiro swears he'll wake him up more often. When Baymax opens his eyes again, though, he knows the promise hasn't been kept.

Hiro looks the same, and his voice even sounds the same, but the way his haunted gaze darts around the room gives Baymax pause. He very deliberately does not ask how long it's been, how long the boy has had to live with his own thoughts and fears, and instead asks what he's planning to do now, without school or hero work to occupy his time.

Hiro doesn't say anything for a while. "I don't know," he finally sighs. "I don't know."

He has that sense again, that something should not be the way it is, and it leads him to put one arm around the boy's shoulders. The sentiments he wants to express are difficult to put into words, but he's able to say that he wishes things hadn't turned out like this. Hiro shakes his head and doesn't say anything. Hesitating, unsure of how comfort would be best shown in this situation, Baymax quietly tells him he's sorry about all the pain in his young life.

Still silent, Hiro brings his hands up to his face, then takes a few shuddering breaths. "This is all my fault," he says suddenly, and then there's nothing left to keep him from crying, so he doesn't try to stop. "I- I told you to-"

Baymax has no idea what to say, so he doesn't say anything, only drawing him into a hug while the tears spill out along with the words- the awful, horrible memory that falls like a stone and leaves Baymax wishing it all could have been different.

"I'm so sorry, Baymax," he sobs, and then he's repeating it again, that it's his fault, it's his fault and he let everyone down and he thought revenge was what he wanted but it just left him sick and torn apart and now it's worse than before, because now he's a monster and if Tadashi was still here he would hate him-

Baymax freezes.

Pulling away, he looks down at Hiro and asks if he really thinks that's true.

He only glances up for an instant before closing his eyes again and holding his head in his hands, but it's enough time for Baymax to see terror. A quick, inaudible scan translates his brain activity into data he already suspected: Hiro is fiercely, almost savagely afraid, and at the moment, he can't keep his thoughts away from that fear, because the past and the present and the future are all bearing down on him.

Baymax makes another judgment call.

But when the video is playing, and Hiro is statue-still at the sight of his brother's face, he hears Tadashi say, "You're going to help a lot of people." Hiro flinches, and it's as if Baymax has been hit by a thunderbolt, because he realizes that he just vindicated his deepest fear.

He reminded the boy of his actions, then juxtaposed them with Tadashi's original intent, and more forcefully than he ever could have with words, convinced Hiro that he has forsaken his brother.

Panicking, Baymax tries to backtrack, tries to assure him that Tadashi loved him and would never be ashamed of him, but Hiro looks at him with blank eyes and utters the codewords, and Baymax can only watch his own vision fade. His last thought before deactivation is that he has utterly failed.

[]

Years pass.

They must, because when the systems and circuits flare to life, and Baymax finds himself in the attic of the café once again, he's facing someone he's never seen before. Then the figure speaks, and he realizes it's Hiro.

To say he looks older would be an understatement. Everything, from the shape of his jaw to a shorter haircut to a more steady expression, has changed. "I'm leaving," he says flatly. "Thought I should, you know, say goodbye."

Then he pauses, looking more embarrassed, and rubs the back of his neck, and just for a second, the old Hiro is back. "And, uh, sorry I didn't talk to you in a while. I guess I just..." He trails off, and something in the mask slips, and Baymax can see that lost look in his eyes again, but it passes quickly.

It's a lot to process, and Baymax doesn't say anything for a while.

Hiro explains that he's already told his friends, and no, he doesn't know exactly where he's going yet, and yes, he's already packed plenty, even though Baymax hasn't asked either of those questions. He also tells him he'll be stationed at the school from now on, where the others can continue Tadashi's research and maybe even just take time to talk once in a while, whenever they need- in Fred's words- 'a big, poofy friend to hug'. It's strange to hear him talking like this, as if he's already gone, and it strikes Baymax that Hiro probably already thinks this way. Maybe he's thought it for a long time.

Casually, like it's an afterthought, Hiro mentions that Aunt Cas already knows about Baymax, so there's no more need for sneaking around.

He pauses, and because he knows the answer, asks if Hiro has told her that he's leaving.

A half-smile fades quickly, and Hiro looks down. "Actually, I was kinda hoping you'd tell her."

Baymax gently puts his hand on his shoulder, and even though he's not as short as he used to be, Hiro still has to look up to meet his eyes. "Yeah," he says quietly. "Yeah, it should be me, huh?"

It should, but Baymax doesn't say it, because more than anything, he just wants to know why Hiro has to leave at all. When he asks, Hiro shrugs, but it's obvious he's put a lot of thought into this. "I can't... I can't stay here, man," he says with a glance over to the window. "Not after-"

He stops, yet looks completely calm, and after a second, turns back to Baymax. "I need you to know something. I don't- I don't blame you at all."

There's no anger in his voice. A quick scan tells Baymax that his brain activity is normal, and when Hiro speaks, it's with confidence, not shaded by self-loathing or pity or anything else. "It's my fault," he says. "Don't ever blame yourself. Not once, alright?"

He can't do anything except nod.

Hiro thanks him, and almost smiles, and trudges down the stairway, and slips away from Baymax's world without ceremony.

It's not until much, much later, when Hiro has already left and the others decide to finally tell Baymax what they saw, and he nods along as if he's hearing it for the first time, that he begins to understand how foolish it was to pretend he had no memory of that day at the lab.

Because, he realizes, Hiro knew he was faking the whole time.

GoGo is the only one still in the school's lab- she stares at him for a while before finally asking how he's holding up, and it takes him a second to figure out what she means. She's asking about his emotional state, probably worried he might react badly to the news. It strikes Baymax as very... human.

Weighing his words, he tells her that he regrets his actions.

"It wasn't your fault," she says, without a hint of emotion in her voice. "It was Hiro's."

Technically true. Factually accurate. More than ever before, Baymax can't escape the sensation that these are no longer sufficient.

"I mean, I get why he did it." GoGo crosses her arms. "Doesn't make it right. And I think he knows it, you know? That's probably why he left."

It was wrong. It was wrong, but... Baymax pauses. But what? He can't grasp this particular idea, and he doesn't understand why- it's not logical at all. Against reason, something in him wants to defend Hiro. Even when, perhaps, he should not be defended.

The line between thought and emotion, even for someone incapable of either, appears to be blurring.

GoGo sticks around, and the conversation eventually steers away from Hiro. Baymax is grateful for the company, and she doesn't mind talking about developments in her life over the last few years, and what the others have done, too. Soon, their only shared experience- the superhero team- becomes the talking point, and he even gets her to laugh over memories of Fred's and Wasabi's antics. It's strange, but attempting to have this sort of friendship with anyone except Hiro still feels unnatural.

Out of nowhere, she asks if he ever thinks about starting the team up again.

He hasn't, truthfully. But the question seems to echo, and soon he's focusing on his never-used analyses of the city's crime rate and infrastructure and demographics. There's even more tech at the college, now, and if the rest of the group wanted to come back, there's no reason they couldn't...

Baymax stops. There is a reason, of course. He looks GoGo in the eye and tells her he doesn't know if he could do it without Hiro.

She nods, looking down at her feet- when she speaks again, it's in a softer, more thoughtful tone. "Do you ever wonder what it would be like? If we hadn't... you know."

Strictly speaking, Baymax shouldn't know what she's referring to. As a robot, he isn't inclined to speculation of any sort.

He tells her yes.

GoGo smiles. "Maybe if we never went to that island... I don't know." She looks up, at all the machinery and tech and gadgets in the lab space, and waves her hand. "All this, it's to help people, right? That's the goal, anyway. And we were finally gonna do that, and..." She blinks. "I was happy."

It's been a while, but Baymax is aware of it again, the quietly insistent sense that something is wrong.

"Couldn't we try?" She scowls, glancing away. "Even without him. Can't just let it all go to waste, right?"

Right.

This time, Baymax knows he shouldn't have any notion of agreeing, but he doesn't care. Maybe they can try again.

"I hate..." Frustrated, she puts her hands on her head. "...not- not knowing what to do. I hate it."

He can't comfort her. He can't say anything to make it all seem simpler, or easier, or clearer, but he replays her words over and over in his memory, stunned by how similar they sound to his own processes not long ago. And when she leaves, when she says the codewords for him to deactivate and promises that someone will wake him early enough to help out with classes, and when Baymax closes his eyes, he wonders if his time with Hiro has forced him to adopt human traits.

After all, uncertainty and worry hardly seem robotic.

[]

The next time, Baymax waits a second before opening his eyes.

He hears the bustle of activity signaling a normal day in the science lab. Someone, probably Fred, is tapping against his head and asking what's taking so long, but he still waits.

The sense is there, gnawing at him, and he doesn't know how to fix it. He may never know. He accepts it.

Mistakes were made, and the past will continue to haunt him. He accepts it.

He failed his charge from Tadashi, to keep Hiro safe. He can't accept that, but maybe one day, he will. And maybe that same day, years in the future, when classes have arrived and studied and moved on, and Baymax and the others have helped people and tried to do good for the world- maybe then, a familiar face will appear in the city.

It won't be a thought, exactly. Or a feeling.

But somehow, it will be right.