Castiel is on his third bus when she approaches him.

The bus is crowded, and the seat beside him is one of the few open ones left. She slides into it, stuffs a messenger bag at her feet.

For the first time, he looks away from the window to evaluate the woman beside him. She glances up, the eye contact awkward and fleeting. Her smile is brief, all politeness and no weight. Castiel remembers Dean's lessons in body language and drags away his eyes. Dean would make a comment about the staring, if he were here.

Dean. The pain throbs deep in his chest, a kind of pain Castiel isn't supposed to feel as an angel. He hurt the best friend he's ever had.

Knowing Dean, Castiel will be forgiven soon. But Castiel isn't sure he can forgive himself.

For thousands of years he was pure, righteous. Castiel followed the word of Heaven and no other. But then he seared his handprint onto Dean Winchester's soul, and his entire world changed.

Before, Castiel never questioned Heaven. His world revolved around Heaven, tied so closely to the archangels that he could see no other way of life.

The bond with Dean Winchester severed his ties with Heaven. Suddenly Castiel was tied to this man, this simple mortal with a penchant for alcohol and Led Zeppelin. Suddenly the world was shades of gray.

Castiel was lost without his bond with Heaven, and he made mistakes. He was led astray by Crowley, then again by the Leviathans. He will never be able to compensate for those mistakes.

Yet this mistake is his worst yet. Castiel cannot face Dean. He remembers how the man looked, eye bruised shut, blood dripping from his mouth, arm broken. He cannot accept Dean's forgiveness, cannot go on a hunt as if everything is back to normal.

Besides, there is the angel tablet to think of. The tablet is heavy in Castiel's lap, heavy with purpose and intent and guilt. Naomi will surely kill him if she finds him. He must run, and run quickly. Hence the bus.

Lost in his own thoughts, the countryside passes Castiel's window quickly. He makes no conversation with the woman beside him. The bus empties, but she doesn't leave her seat. Castiel does not mind. The heat beside him feels comforting. It grounds him, reminds him that he is just like her now. He feels more human than ever right now.

He misses Dean already.

After some time, she looks up from her book. She opens her mouth to speak, hesitates, then says, "So, where are you going?"

Castiel turns from the window, slowly. He doesn't respond, simply stares at her. Humans don't ever talk to him, besides Dean and Sam. He doesn't understand. This stranger has started a conversation on a bus in Iowa and Castiel has no idea what to say.

"Far away," he says, because that seems the best answer. In fact, Castiel has no idea what his final destination will be. All he knows is he needs to be away from Dean and away from Naomi and away from Crowley.

She smiles, and he isn't sure what is so funny. "I suppose I'm the same. My name's Kate."

Castiel nods, unsure of what to say next, and turns back to the window.

She persists. "Now is the point in the conversation where you tell me your name."

It reminds him of Dean, the gentleness in her tone, the playful jab at his social skills.

"I am called Castiel," he says simply, eyes still focused on the horizon.

"Interesting name."

"Some call me Cas," he adds. Dean was the first man to call him that, but then the name spread like wildfire. Even the angels call him that now. Castiel is not sure how he feels about that. But it seems acceptable for this woman to know the nickname. She is human, and she is warm.

Kate nods and goes back to her book.

She is one of the seven billion people Castiel fought so hard to save three years ago. It comforts him to know that she is here, breathing and smiling, because of him and his friends. Humanity is worth falling from Heaven, he thinks.

Lost in thought, he misses her next words. But he sees her mouth moving, and so he says, "Excuse me?"

"I asked where you were from."

He almost says Heaven. But Dean would scoff at that answer and tell him to lie. "Lawrence, Kansas." It feels right. Castiel is here, on this bus, wings clipped, because of Dean, however indirectly. His roots are Dean's roots.

"No kidding! I'm from Wichita."

Castiel flips briefly through his textbook knowledge of Earth and recalls that Wichita is a city in Kansas. He will never fully understand how humans connect with people like themselves, people from the same city or state or country. Borders mean nothing. He will never fully understand humanity.

(He understands Dean Winchester, inside and out. He rebuilt Dean Winchester from scratch, counted freckles and shaped hands. Castiel raised him from Hell. That bond is not easily broken, not by Naomi, not by anyone.)

When he contributes nothing to the conversation, Kate says, "You seem distracted."

He nods. "I am rather busy."

"Doing what? Examining the countryside? You're just staring out the window."

"I am on an important mission."

She grins and closes the book. "Secret Service, yeah? Let me guess – you're headed for New Mexico?"

He doesn't understand the reference. "I am not affiliated with your government."

Kate giggles. "You talk weirdly. Very formal."

"So I'm told."

"You don't talk to strangers often, do you?"

Not humans, he doesn't. He occasionally speaks to demons before he exorcises them. He hears the chatter of angels in his head, a constant reminder of all he's lost. Conversation with a kind woman on a bus is refreshing, really.

He shakes his head. "And you? Do you frequent cross-country buses often?"

"No. But I've just gotten… tired of life in Kansas. I'm going to the west coast to start fresh. Clean slate, you know."

How Castiel wishes he could have a clean slate. He almost had that once, as Emmanuel Allen, but that life is gone now. "I could use that."

There's a beat of silence, and then she asks, "From what are you running?"

He looks at her then, really looks at her. "How did you-"

"Takes one to know one." She looks back. Her eyes are plain, brown and a little too close together. Still, there's a spark of curiosity in them. Human eyes, no matter the color or shape, carry life in them.

(Dean's are green some days and brown other days, and sometimes Castiel can feel their gaze on him, hot and cold at the same time.)

She looks away first, with a small smile. "C'mon, answer the question. Unless you really are Secret Service or something and aren't allowed to say."

Dean, in this situation, would lie without hesitation. Dean always deflects questions like this, covers them up in a shrug and a half-hearted joke. It is one of his faults, and one of his virtues.

Castiel does not have the same talent in deceit. "I betrayed a friend. I came very close to doing something… unforgivable. And so I ran away."

"That's a good reason." She nods thoughtfully. "You had the self-control to leave before too much damage was done."

"I am a coward."

"No, I think you're very brave. If you don't mind my asking… what did you do?"

Now she digs too deep. Castiel looks back to the window, shifts nervously in his seat. He rests his hands on top of the stolen tablet.

"I'm sorry, I didn't mean to pry." She ducks her head, and he recognizes the reaction as embarrassment.

"I was under the influence of someone. They wanted me to hurt a person about whom I care very deeply, and so I did."

She laughs. "You're very vague, you know."

"I am, in fact, aware of that. But I do not feel familiar enough with you to tell my story in full."

"Understandable. You're a very logical person, Cas."

The name feels foreign in her mouth. It feels wrong.

"What do you fear?" he asks her. She said she was running too.

Kate shrugs. "Death, I guess. I'm afraid of dying."

He smiles slightly. "It's not nearly as bad as you fear."

"Like you would know."

He fixes his eyes on her. "I have died three times."

She laughs like it was a joke. "And what was it like?"

"Quick," he says. "Except for the last time. The last time was slow, torturous." He remembers marching into the river, unable to control his own vessel. He remembers the desperation in his lungs as his air ran out. He remembers his limbs slowing, he remembers his heart stopping.

She looks at him differently, now. "Are you mental?"

"I was, once." He shrugs.

She shifts in her seat. Castiel is not very good at recognizing body language, but he recognizes this.

"Am I alienating you? I've been told I'm not very good at conversation," he says.

Kate laughs nervously. "You're a little weird, Cas. It's a bit scary."

"Yet you continue talking to me."

"I'm curious," she says. "You're alone on a bus with nothing but a duffel bag."

"As are you," he remarks.

"True. Maybe that's why I'm interested in you."

"I don't understand."

She raises an eyebrow. "Do I have to be any more obvious?"

"Yes."

Kate sighs and mutters, "Figures, hot single guy is a socially inept basket case."

"My temperature is the same as yours," he says. "No, wait. Dean uses that term to refer to voluptuous women." He cocks his head to the side. "But I am not a voluptuous woman."

Kate laughs, really laughs. "It means I think you're attractive. I was trying to flirt. Clearly you didn't get it."

Finally the meaning of her words dawns on him. "You made conversation because you were interested in me sexually."

"Well, when you put it that way…" She throws up her hands in resignation. "Nevermind."

Suddenly his jacket feels a little too hot, the bus a little too stuffy. "Oh. Excuse me, I didn't mean to- I don't- I wasn't trying to-"

"Are you getting flustered now? That's adorable."

His mouth opens and closes several times. Castiel never knows what to say in these situations. Dean would have the perfect line prepared, a casual deflection of the girl's interest, but Castiel is not nearly as eloquent.

"Seriously, it's fine. I wasn't too invested in it. Just thought you were cute. Let me guess, you've got a girl waiting for you at the bus stop?"

Castiel shakes his head. "No, I have no one waiting for me."

"No girlfriend?"

He thinks briefly of Meg. They had something, but it would never have amounted to much. She was more attached than he.

He felt her death, even from miles away. Meg was good, near the end, and she was his friend. But Castiel was not in love with her. He does not ache with longing for her.

When he hesitates to respond, Kate prompts, "There's something you're not telling me."

"There was a woman. She expressed an interest in me, and I reciprocated. But now she is dead and I don't feel anything."

Kate lets out a quiet breath. "I'm sorry for your loss."

Castiel shrugs one shoulder as he's often seen Dean do. "As I said, we had a connection but nothing more."

"So maybe you just don't like girls. Do you have a boyfriend, then?"

He shakes his head, but of course Dean comes to mind. Dean is always on his mind. "There is a man. His name is Dean. We have a… bond. Much stronger than the one I had with Meg. The kind of bond that transcends lifetimes. My life revolves around him. I think that is what humans would call love.'"

"Okay. So you're gay. No wonder you rejected my advances. No big deal."

Castiel looks at her. "No, I am not gay, or straight, or anything. Dean is a separate category entirely. He's everything."

"So he's your soul mate?" She smiles slightly.

"My grace is seared onto his soul. I am forever devoted to him." Castiel wonders briefly if that means the same thing. He doesn't quite understand human love.

A look of understanding dawns on Kate's face. "He's the person you betrayed."

Castiel sinks down into his seat, dropping his gaze. "Yes."

"And now you can't face him because you think he won't forgive you?"

Castiel shakes his head. "Dean will forgive me, in time. I cannot forgive myself. I've betrayed him one too many times in the past few years. Yet somehow he still believes in me."

"Sounds like a helluva guy. You want my advice?"

"Yes." Castiel has always been inept when it comes to love.

"You forgive yourself. Everybody makes mistakes."

"Not like mine."

"You said you were under the influence of someone else. It wasn't your fault you hurt him."

"Yet I was the one who threw punches. I nearly killed him."

"You nearly-" She stops at that, and gives him the same look she did earlier when they discussed death. "Are you, like, a murderer or something? Should I be scared?"

"I won't hurt you," he says. "You are kind. You have no reason to fear me."

"You're not helping."

He sighs. "Then go; find another seat on this bus. You started the conversation, you can end it just as easily and leave me to my reflections."

"Yeah, but…" she hesitates. "You look like you could use some kindness."

Castiel looks up at her. "And why are you offering it?"

She turns away from his gaze. "You, uh, you never asked from what I was running. I just… I don't have a lot of time left, and I figured I'd use the days I had making others' lives better."

Castiel looks at her, really looks at her for the first time. He'd been distracted before, too focused on his own burdens, to notice hers. Castiel can read a person's history from the size of their pupils and the way they hunch their shoulders. He never thought to read hers.

He notices for the first time how thin her brown hair is, how hollow her face looks. "You were diagnosed with a brain tumor."

She nods. "Yeah, uh, a couple of days ago. I've got about a month left, they said."

"So you dropped everything and headed west. What is it you humans say? Carpe diem?"

She grins, lips pulled taut and thin. Castiel's appalled he didn't notice the cancer before. "Yeah. Kindness is really all I have left to give the world."

On days like these, Castiel is reminded of why he saved humanity. Humans are beautiful, God's greatest creation.

He stares at her openly now, ignoring Dean's rules. "You are a wonderful person."

Her eyes widen very slightly. "Thanks. No one's, uh, told me that before."

"But what you are doing – kindness for the sake of kindness. It's inspiring."

She shrugs. "Even at your lowest point, you can always do something kind for a stranger. Give them advice, money, whatever. I have nothing left, nowhere to go. So I sit next to a stranger on the bus and ask him what he's running from, flirt a little, and hope it all works out. It's fulfilling. That's my philosophy, at least."

Castiel nods slowly. Before, when he traveled the country healing the sick, he considered it penance for his sins. But this woman is right – being kind is not a punishment. It is her way of giving all she has to the world.

If anything, Castiel can do the same. He can devote himself to humanity, devote himself to Dean Winchester. He can be kind.

He looks out the window again. In the next town over, there's a hospital full of the sick. Suddenly, he has a destination on this journey.

First though, he must repay the kindness bestowed unto him.

"Thank you," he says. "I have to go now."

"Wait, what? What do you mean, you have to go? The next bus stop is an hour away!"

He reaches out and touches her forehead, feels the tumor dissolve under his fingers. This woman will live a long, full life.

Kate flinches against his touch. "What are you doing?"

"I am being kind," he says.

She blinks, and when she opens her eyes again, Castiel is gone.