Contrary to popular belief, Donna Noble was not all-knowing, and travelling with the Doctor had only made that more apparent.

It was amazing, of course, absolutely brilliant. The best thing to ever happen to her. There were moments, though, these days, when she felt so lost and clueless—when her Time Lord companion went on a spiel about quantum mechanics and the space-time continuum, or ranted about the murderous exploits of an alien race from a far-off star system, or tried to teach her which parts of the TARDIS did what. When she was left to solve a history-altering problem on her own, or had to negotiate a peace treaty between species whose names she could barely even pronounce. But nothing about her travels could leave her in the dust so completely as the Doctor himself.

He was normally so bright and cheerful and curious. She'd seen him stop and gape at a particularly gorgeous starscape, despite having surely seen a billion, bounce on the balls of his feet upon spotting a rare plant, offer a hand time and time again to people who, moments before, had been trying to kill him. No one had his love for the universe, his appreciation for every single being in it, his desire to see every nook and cranny he could get to in his little police box. Donna had never met such an incurable optimist, and she greatly admired that about him.

She could scarcely believe that the Doctor before her now was the same person.

He was curled up on his bed, faced away from her as she leaned against the doorframe to his room. Normally, he would have shut and locked his door, but it seemed he couldn't be bothered. The room was a mess, even more so than usual, from the few times she'd been in there before, papers and spare parts and articles of clothing scattered all about. He was half-tangled in the bedclothes, as if he'd tossed them haphazardly over himself and given up, and he clutched a handful of blanket tightly to his chest. Though he didn't acknowledge her presence, she knew he wasn't asleep; he rarely slept, especially around other people, especially as of late. Donna would have rathered he simply be asleep.

On these sorts of days, it seemed, he just couldn't bear to get up and go about his routine, to pretend everything was fine. He wasn't tired, exactly, not in a way that could be helped by sleep, but he appeared to have run clean out of energy. It was like the weight of the universe sometimes got too heavy for his skinny little shoulders. Had he always looked so… so crumpled? So small? Donna didn't think so.

She had nothing but sympathy for him—who wouldn't have days like that, if they'd been through what he had?—but she was rather clueless when it came to this aspect of their friendship. He always knew what to say when she was upset, and she had absolutely no idea how to help him in return. And it pained her, not being able to take away his suffering. He deserved no less than that.

Regardless, she knew couldn't just leave him. There had to be something she could do.

"Doctor?" she said quietly. "Can I come in?"

The Doctor didn't speak, didn't move beyond a tiny, hesitant nod. Donna stepped inside, almost afraid to break the silence, and sat slowly on the foot of his bed. She didn't try to touch him—she knew better, now, than to touch him without permission on a bad day. Sometimes it made him flinch away, startled, and he would blink as if expecting a blow, and his hands would tremble for a second as he fought against his instinctual reaction. She remembered the first time that had happened, remembered feeling sick with anger as she realized why, wanting nothing more than to get her hands on whoever had taught him to do that. She'd barely managed not to hug him and hold him until he stopped being scared: an apology on behalf of the people for whom he weathered all of this.

She glanced briefly in his direction before returning her gaze to the wall in front of her. He'd been crying, his eyes red and glistening with tears. She shifted her position so she faced away from him, giving him his privacy, and a sympathetic pain settled deep inside her chest. Her shoulders sagged.

"Oh, Doctor," she sighed. "I'm sorry."

There was no response, but she didn't really expect one.

"Do you want to talk about it?"

After a long pause, she heard him take a ragged breath. "No," he whispered. "Not really."

"Would you rather I left?" Though she would go if he told her to, she desperately hoped he wouldn't. She didn't like him being alone when he got like this.

"If you wouldn't mind, I… I'd like it if you stayed."

Relief brought a tinge of a smile to her lips. On a hunch, she stood up and grabbed the chair belonging to his desk, carrying it over next to the head of his bed. She sat heavily in the chair, her gaze sweeping over his body. He looked terribly small, all curled up like that. He hadn't even bothered to change out of his suit; that was a sure sign he was having a really awful day.

Instinctively, she reached out to squeeze his shoulder, then remembered herself and paused. "Is it alright if I just touch your arm here?" she asked.

"Yeah." He sniffed, and pulled the sheets tighter against his chest, almost hugging himself. There was something in his tone that made the word sound like a plea.

She placed a hand on his shoulder and just stayed there, in silence, for several long minutes, playing with the fabric of his jacket under her thumb. She felt terrible for him, and worse knowing that he'd hate for her to feel bad because of him. Even when he was too exhausted to get up, he couldn't stand being a burden. Bloody alien, thought Donna, staring sadly at his prone form.

Suddenly, the quiet felt totally and utterly wrong. It was never silent around the Doctor. He should be talking nonstop about something she couldn't make sense of. Anything, really.

Well… she could do talking. She was rather proficient at talking. And she couldn't think of much else to do, so talk she did.

"You remember last time we visited my family?" she said. She didn't give him time to decide whether to answer before she continued. "It was so cold, I'd thought you'd landed in the wrong place again. And you didn't even notice, just went wandering off after that signal, or whatever it was you were tracking—you really should start dressing for the weather, y'know, Mum couldn't figure out how you didn't get frostbite."

"Donna," the Doctor mumbled quietly, like it was costing him greatly, "what're you doing?"

"Nothing. Just talking. Is that alright?"

He thought for a moment. "Yeah. 'S good."

"Good." Donna gave his shoulder a gentle rub before moving her hand to play with his hair. He stiffened for a split second before relaxing under her touch, and she knew she hadn't overstepped her bounds. "I'm not sure I ever mentioned… When we went out to get groceries that day, Mum found a cat under the hood of the car. He was hiding from the snowstorm, poor thing, half-frozen already. Of course, Gramps insisted we bring him inside to warm up. Mum's not really a cat person, though, so she wouldn't let him keep him. I think he ended up giving him to a family friend." Donna smiled fondly, remembering that day. Wilfred had been thrilled to have the little kitten in his care, even just for a few hours.

There was a beat, as she thought up something else to talk about.

"Oh, and remember our trip to Saris for that part you wanted?" she continued after a moment. "For the food replicators? Funny place. I figure, if a combination convenience store and gas station somehow spread across half a planet, it would look like that. Y'know, I saw this one plant there that had like five different colours of leaves and a bright purple stem. And it had these hairs all over it, but the repairman said I couldn't touch 'em or I'd get all itchy. Wish we had stuff like that on Earth."

"Poison ivy," remarked the Doctor, voice muffled by his pillow.

"Not that part, you prune," she laughed. "Oh, and by the way, I think the replicator that sometimes appears in that one corner of the library still isn't working quite right. I asked for a tea and it gave me… well, I don't know what it was. It might've still been alive. It was sort of tube-y? And squishy, like a sea cucumber. But with suckers."

The Doctor gave a soft little chuckle at that, and Donna smiled. Maybe all he needed was a bit of unconditional company, someone to exist near without having to get up or act happy or even respond. So for the next half-hour, give or take, Donna just sat by his side and talked. She told him all sorts of pointless, lighthearted stories—that time the TARDIS wouldn't let her out of the simulation room for four hours, Wilfred's account of the first time he'd met the Doctor, what clever thing she'd snapped at the octopus bloke who said humanoid brains were too simple to understand transference calculus—and he listened in silence, for the most part, occasionally offering an equally pointless comment or a quiet laugh. When she had to pause and think of something new to say, he waited patiently, secure in the knowledge that she was right there next to him and wouldn't be going anywhere.

And, little by little, Donna saw him pull himself away from his thoughts and start enjoying himself. At least a bit. Sometimes, she couldn't believe how incredibly resilient he was; the stuff he'd gone through was just unfathomable to her, and somehow he was still the kindest, most compassionate, most amazing person she'd ever met. He hadn't always been comfortable with her seeing him upset or scared—she suspected trying to hide it had only made his mood worse, because he used to disappear into the TARDIS for a day or more when his depression acted up—but she was glad he had warmed to the idea. Contrary to his belief, it only increased the amount of respect and admiration she had for him.

Eventually, when the laughter after a particularly good tale had died down and Donna couldn't think of something to follow it, she let the conversation trail off into silence, moving to take the Doctor's hand in hers.

"Do you think you're ready to get up?" she asked, gentle, unpressuring.

The Doctor hesitated, considering.

"You don't have to," she murmured, tracing little circles on the back of his hand with her thumb. "If you don't want to, I'll stay. Don't worry. But I figured you might like to go to the den, have a cup of tea, put on that show about cosmology that you like."

He shuffled around to face her, frowning. "You hate that show."

"I don't hate it. I like the pictures of stars."

He couldn't help the corner of his mouth lifting in a hint of a smile. "Sure. Sounds good."

With a final squeeze of his hand, Donna stood up and moved the chair back to his desk. Slowly and stiffly, the Doctor untangled himself from the bedclothes and pulled himself to his feet, stretching limbs that probably hadn't been moved for hours. He didn't seem to want to meet her eyes, clearly embarrassed that his companion was having to drag him out of his room.

Shaking her head at his foolishness, Donna walked back towards him and wrapped him in a hug, surprising him for a second. Then he hugged her back, just as ardently, and took a shuddering breath; he swayed back and forth ever so slightly, the way he always did, almost as if comforting himself.

Donna tightened her grip on him, nestling her head against his shoulder. "I love you, Doctor," she whispered. "It's gonna be alright. It's gonna get better. I promise."

She felt him shudder as he fought to keep from breaking down. "Thank you," he rasped, and cleared his throat. "Love you, Donna."

When they pulled apart a moment later, the Doctor was wiping tears from his cheeks. He laughed. "You really are too good to me, you know," he mumbled, eyes downcast. "You don't have to do this."

An ache tugged at her heart. He didn't need to feel guilty for accepting her help, not on top of everything. She was happy he'd managed to get out of bed, but his eyes were dull and mournful, almost too tired to be sad, and she could tell he was a painful thought or two from lying back down and giving up for the day.

"Stupid Martian," she grumbled, and that seemed enough to settle the matter. She took his arm and, before he could talk himself down, tugged him out of the bedroom and down the twisting hallways to the den. He sort of lagged behind, lacking the energy to keep up with her, but he went. And she was very glad of that.

They got to the den, and Donna suddenly stopped him outside the door, holding him in place by the arms. He raised an eyebrow.

"I know… I know this isn't easy for you," she said, glancing up to meet his gaze. "I'm very proud of you, Doctor. Thanks for letting me stay."

After a moment of surprise, his worn expression melted into an affectionate grin. "You are brilliant, Donna Noble," he proclaimed softly.

Suddenly he looked worlds better, just a little bit of that old enthusiasm shining in his dark brown eyes. Donna felt something unknot in her chest; she hadn't even realized she'd been so anxious for him until she knew he was going to be alright.

She pressed the button next to the door and it slid open to the cozy, comfortable room beyond. The Doctor wandered inside, her just behind, and flopped dramatically down on the sofa. He got a thoughtful look on his face as she sat beside him and grabbed the remote from the coffee table, flicking through the channels.

"Do you remember Penumbra?" he asked.

Donna smiled.