There was something missing. It was as if all the pain and suffering of his 900 years had finally caught up with him and left him void of any and all happiness that had still remained.
A tense silence stretched out between the Doctor and Donna as he fumbled with the TARDIS key and eventually stumbled inside, with his fire-haired companion following closely in suit.
He took leaden steps to the console and punched a few buttons to initiate the TARDIS dematerialization sequence.
And that was that.
For about a week, anyway. Even as time distanced them from the incident on the diamond planet, the Doctor's normally energetic and bright chocolate brown eyes remained dull and glassy-looking.
It seemed that his recent possession had drained him of all energy; he was barely able to scrape up enough motivation to continue showing his companion the wonders of the universe.
Donna on the other hand couldn't remember ever having stayed in the TARDIS for so long and she had practically been given free reign over when and where they travelled. Eventually, she couldn't take it anymore, and decided to suck it up and say something.
"Spaceman?" She placed a tender hand on his shoulder, causing him to flinch, "You alright?"
"Fine..." He ground out, his voice raw and cold and melancholy.
"You sure about that?" She pried gently.
"No." He hung his head dejectedly and took a shaky breath, "Not really. But it's alright, I will be..."
"Not very reassuring, Doctor. When was the last time you got any sleep?" Badly masked worry dripped from her words.
The Doctor tensed visibly. He desperately wished Donna would stop talking about it. His mind could barely skirt his recent possession without his stomach tying itself in knots and making him feel horribly ill.
"Doesn't matter." He mumbled stiffly before quickly trying to change the subject. The unhealthy ashen, pale color of his skin and dark purple smudges underneath his eyes begged to differ.
"Yes it does! You can't just keep going on like this, you're gonna make yourself sick!" Donna insisted.
"Um, might..." The Doctor swallowed thickly as nausea threatened to overwhelm him. "Might be a bit too late for 'make'..." He fought to continue speaking "Try...try 'made'."
He collapsed onto his hands and knees before he emptied the contents of his stomach onto the floor.
As he was sick, he became vaguely aware of one of Donna's hands on his shoulder and the other rubbing his back while she murmured comforting words into his ear.
The Doctor leaned back against the console and coughed a few times before he drew the back of his hand across his mouth.
"'m sorry..." He muttered pathetically as Donna slipped her hand under his sweat-drenched fringe to check his temperature.
"No, it's okay, it's okay...C'mon, let's get you to bed." She sighed as she looped an arm around his skinny waist and hauled him to his feet. They made their way through the corridors of the TARDIS slowly, Donna shouldering most if the Doctor's weight.
Not knowing where the Doctor's bedroom was (or if he even had a bedroom), Donna decided on taking him into her bedroom. Once they finally reached her bedroom, she dragged him to her bed and shoved him on top of it.
Once his prone form was splayed out across the bed, she removed his jacket and began unbuttoning his shirt. Turning around to toss his clothing over the back of a chair, she noticed a pair of men's pajamas neatly folded on top of her dresser that she was sure hadn't been there a moment ago.
The Doctor appeared to be sleeping, and Donna hated to wake him, but she didn't necessarily want to undress him while he was unconscious.
"Doctor, c'mon, you've got to wake up now..." She whispered, shaking the sleeping Time Lord's shoulder gently.
The Doctor moaned softly as his eyes fluttered open and they looked even more glazed over than earlier.
"Donna?" He managed with a rough, cracked voice and propped himself up on his elbows.
"Shh, shh, you can go back to sleep in a moment, you've just got to put some pajamas on." She said reassuringly. Despite his poor state of health, Donna couldn't resist lobbing the mass of fabric directly at his face.
Donna padded across the plush carpet to the en suite bathroom and closed the door behind her, giving the Doctor some privacy to change.
After fiddling with her vibrant hair in the mirror for a few minutes, she decided that she had given him enough time to shed his clothes and change into the more comfortable options provided by his beloved police box.
The heart-wrenchingly adorable sight of the Doctor sitting on top of the bed in a pair of stripy pajamas greeted her as she reentered the room.
"Alright, let's get you tucked in."
The Doctor stood politely away from the bed to allow his friend to turn down the covers for him. The large, soft mattress was looked incredibly inviting and he was glad to collapse on top of it and let Donna pull the duvet up to his chin.
She turned towards the door to turn off the light when the Doctor uttered a single, soul-crushing statement.
"Please don't leave me."
Donna turned on her heel to face him and nodded understandingly, afraid that if she spoke, her voice might crack and she would sound as choked up as she felt. She grabbed the desk chair where she had tossed the Doctor's shirt and jacket and slid it over towards the bed.
"D'you want to talk?" She tested her voice, happy to find that she didn't sound like she was about to cry.
"I'm so scared Donna." He whispered, curling in on himself so he was no more than a little ball underneath the covers. "I can't sleep or else I have nightmares. I'm so scared it's going to find me and take my voice again." He admitted, eyes glistening with unshed tears.
"Hey, hey it's okay." She murmured, "You're safe, you're safe here in the TARDIS, and if anything tries to get near you, I'll give them the bollocking of lifetime."
The Doctor smiled for a brief second before his features turned somber again.
"Try and get some rest, I'll be right here. I promise." Donna said as she reached forward and ran a hand through his unruly hair.
He nodded and closed his eyes, comforted by the presence of his companion as his consciousness ebbed away slowly.
"Doctor! Doctor, wake up! It's just a nightmare!" The Doctor was violently shaken from his feverish, nightmare-riddled slumber by his redheaded best friend.
"Donna?" He managed, tears starting to flow freely down his face. Donna quickly relocated herself from the chair to the bed next to the Doctor and pulled him into a bone-crushing hug and allowed him to sob into her neck.
"It was just a dream, just a bad dream. You're safe, it's all okay, and we're still safe in the TARDIS..." Donna's stream of comforting nonsense continued as she rubbed soothing circles up and down his back, rocking gently back and forth with one hand fiddling with sweat-dampened hair.
They stayed in the same position for a few moments before the Doctor's sobbing faded down to (somewhat pathetic sounding) hiccups and sniffles.
"D'you want to go back to sleep?" Donna asked kindly, pulling out of their embrace and looking into his red-rimmed eyes.
The Doctor sniffled again, nodding and digging the heels of his hands into his eyes.
The rest of the night was rather cyclical; Donna would comfort her friend whenever his nightmares roused his from his fitful slumber and eventually, the gaps between his dreams extended until he was sleeping peacefully.
Feeling rather exhausted herself; Donna crawled underneath the covers next to the Doctor.
She didn't think he would mind.