Donna.
The Doctor looked over at the empty seat next to the TARDIS controls in despair. After having to wipe Donna's memory, he didn't know what he could do. If all of his companions were going to end up like this, either trapped in an alternate universe or not remembering him at all, then what was the point of him even having friends? He sighed and flipped a switch on the top left of the control panel, next to the blue stabilizers.
He couldn't help thinking what she was doing right now. She was probably blabbing to her friend Charity about how stupid her hair looked, or complaining about being a useless temp with no future. The Doctor smiled. She had always thought she was the most unwanted person in the world, but glorious Donna Noble turned out to be the most essential human in the universe. A person who couldn't even find a proper job! He chuckled and sat down in the empty chair, suddenly remembering that Donna would go on believing that she was useless, and his hearts ached, feeling the loneliness swarm through him.
Suddenly, the TARDIS phone rang, and the Doctor jumped. For a split second he thought it might be Donna, or Rose, or at least someone to keep him company. He picked up the phone knowing that the chances of that were impossible.
"Hello?" Ten said hesitantly.
"Doctor? Is that you?"
He smiled as warmth ran through him. Martha's voice was at the end of the line.
He cleared his throat, trying not to sound as sad as he was earlier.
"Yeah, it's me!" He said. "Whatcha need?"
"It's important," she stated anxiously. The Doctor's smile faded.
"What's wrong?"
"Something's gotten out at the intermediate school in downtown London. I don't know what it is, but it's alien and it's killing the kids."
"Oh, my God!" The Doctor began to frantically push buttons, flying the blue box to London.
"Get here quick, I have to go but just, please, hurry!" Martha hung up.
As the phone box landed, the Doctor ran to the school doors and flung them open. He barely took in his surroundings-just that the whole school was in ruins, desks toppled over for shelter- as he frantically made his way to the other side of the school, his sonic screwdriver whirring in his hand.
He checked into every classroom, verifying that people were alright while he continued to sprint down the school.
He was leaning into a seventh-grade pre-algebra classroom when he heard the scream.
As soon as it reached his ears he was running even faster, kicking desks and paper out of his path. He reached a set of double metal doors and threw his body against them and entered the secondary gymnasium.
In the corner, a terrified English teacher was shivering and cowering, fear and worry aflame in her eyes. The Doctor turned his gaze to what she was staring at. Worry crept into his mind as he prepared to act.
An atrociously ugly creature about the size of a horse was in the middle of the gym, slime oozing off of its rough, patchy skin and cracked horn. Its legs were bent as if ready to pounce in the next split second; its eyes (or some version of eyes) were locked onto a young girl with blonde hair.
The girl had her arm stretched out as if she was trying to make peace with the animal. She looked about thirteen, and while she was expertly showing passive signs of friendliness, the Doctor knew better, and wanted to scream at her for being so stupid.
"No! Stop!"
The teen jumped and glared at the Doctor, as if she thought she were more intelligent, and kept pressing on to be acquaintances with the creature, slowly inching forward.
The animal jumped. Green goo slopped on the floor where it had been standing. Time seemed to go in slow motion as the creature almost landed on the girl and would have ripped her throat out if it hadn't been for the Doctor pushing her out of the way just in time. He grabbed her hand.
"Run!"
The girl obeyed immediately and sprinted out the door with Ten; they turned a corner, and another, and another as the beast continued to pursue them with no sign of stopping. As they were about to turn another corner, the blonde on the other side of the Doctor started to tug on his hand.
"I have an idea-follow me!"
Ten was dazed for a moment-since when did his companions tell him what to do? - but then ran after her into an empty chemistry room with cabinets torn off the shelves and beakers smashed on the floor. The Doctor and the girl, together, pushed a desk in front of the door and Ten locked it with his sonic screwdriver. It wouldn't hold it for long, but they needed all the time they could get.
The blonde was in the process of frantically grabbing beakers, acids, compounds and chemistry utensils out of what was left of the cabinets. Ten began interrogating her with questions as she anxiously worked.
"One: Who are you? Two: What in the HELL do you think you were doing back there? And three: What are you doing?"
The girl sighed as if extremely agitated. "One: Anna Transberg. Two: I was trying to see if I could make peace with it. Three: The creature's skin is made of a combination of nucleic acids and sodium sulfate; I noticed it when I first saw it. If I can just make the perfect poison-"she sprinkled a tablespoon of phosphorous into the beaker and gasped. "Yes! This little beauty right here," she lifted the glass, "will burn its skin off."
The Doctor gazed confusedly. "Hang on-how old are you?"
"Thirteen."
"But-"
"Yes, yes, I know, this is high school – college stuff! I'm good at science; I'm the school's chemistry prodigy, blah, blah, blah, let's get on with it." She dragged him over to the back door to the classroom and signaled for him to be quiet. They snuck around the corridor with occasional squeaks of their shoes on the linoleum (which made them catch their breath each time) until they reached the creature. Ten noticed Anna almost quivering with fear, but she quickly regained her posture, exhaled, and splashed the contents of the beaker on the monster's skin.
The creature screamed and screamed an earsplitting sound as its scaly skin erupted into flames; when the noise finally stopped, Anna quickly gave him a high five and he dragged her out of the school.
"What's so interesting about a dumb police box?" Anna crossed her arms over her chest, bored.
Ten grinned. "Oh, you just wait and see." He unlocked the TARDIS and gestured her inside. "Ladies first," he said with a smirk.
Anna glanced at him, incredibly hesitant, but finally gave in to curiosity and stepped in. She gasped in amazement.
"But—What- How in the hell- "
"It's called the TARDIS. It can travel anywhere in time and space, and it's mine."
Anna stared, frozen, at the engine room. She turned to face him. "But it's not possible! I calculated the surface area of the outside, and there is absolutely no possible way even half of your engine controls would fit in here!"
The Doctor stared at her quizzically. "But we were out there for two seconds! No normal thirteen year old could possibly-"
She waved off his sentence. "Yeah, yeah, I know, science prodigy, blah, blah, blah. Now, how exactly do you fly- ow!" Anna's hands quickly flew up to her temples and she squeezed her eyes shut.
Ten instantly put a hand on her shoulder. "Anna? Are you all right?"
"Yeah," she said. "Just- headaches. It's fine, it's going away now."
"Are you sure? Do you want some medicine?"
"No, I'm fine."
Ten stared at her for a moment, then shrugged it off as he began to ramble on about the TARDIS while Anna shook her head in amazement.
He couldn't believe he had found someone so quickly.