He wrote an equation on the board. It crossed his mind how much better Romana was at academia than he was, and how they were learning things at thirteen and fourteen that he could have done in the nursery.
"The Moon has less mass than the Earth, so its gravity affects it less than the Earth's gravity. The Moon has a sixth of the gravity of Earth. On the surface of the Earth an object with a mass of 1 kg has a weight of about 10 N. This means that objects weigh less on the Moon than they do on the Earth. 120 kg weighs 1200 N on Earth. On the Moon they would weigh only 200 N. The astronaut's imass/i is 120kg wherever they are."
A freckly boy at the front put his hand up.
"So, gravity... I mean I know it's a force...but if it keeps us on the ground then is is different depending where you are?"
"Down just means 'towards the centre of the Earth', which is why no one falls off, even if they appear to be...right, there's some questions on this on page ten. I'll be coming around and checking. This is fundamental."
"Doctor Smith? No offence or anything, but what is that on your desk?"
"Fez."
"What?"
"A hat!" He demonstrated. "And yes, I know I'm weird," he pointed to a blonde girl at the back.
"I also noticed you're wearing nail varnish when you're not supposed to, so I guess we're even...!"
She scowled at him.
"Kids today," he mused. "Mind you, that used to be me...not the nail varnish obviously. That was Koschei."
The boy with the freckles looked up from his books.
"Greek?"
"Pardon?"
"Is that a Greek name?"
"Is what a...? Oh, er, yes...he was very Greek."
There was a crash.
"Oh, seriously. This is getting stupid...stop mucking about-"
There was a huge din as all the stools from the back row scraped back or fell back or both. The other rows quickly followed suit.
The Doctor watched as the girl with the nail varnish's friend, a girl with cascades of dark hair began to scream. He ran for the desk and promptly fished the sonic out of the draw.
Her uniform was ripped away. Small patches of skin began to disappear with some force, as if someone was removing small sections of her skin. The inside of her body vibrated, and there was an unholy noise like she was being liquefied from the inside. He whirled round to face the children, who seemed mesmerised.
"Go! Now!" he shouted. "Run!"
She began to writhe, and she seemed to deflate; small, slurries of flesh flecked the floor as it was seemingly being sucked away.
The Doctor climbed on the desk.
"What do you want? If you need help, I can help! You don't have to do this!"
He could smell meat cooking- the friction of the vibrating force had singed its surroundings slightly.
He fell backwards as the pulse spun out towards him and sliced his arm. He felt it began to suck roughly at his wound and began to form others. He growled in pain and placed the sonic to the gash and held it down.
"TIME LORD!" he bellowed, as the pulses collided with the ones from the Sonic. The force whooshed back, imploding, and ripped a small hole in his arm, and crashing into the back wall.
There was some dust in the air from the hole made in the wall.
Breathing heavily, the Doctor hauled himself up off the floor, with his eyes closed. He went behind the row of desks, the longest way possible. Bits of liquefied flesh and blood were scattered randomly, looking stark against the walls- all the science labs were painted white. There was what seemed to be brain matter on the ceiling. There was blood splattered on his white shirt.
He looked down, at what was just skin, covered in blood and small holes where the liquefied flesh and organs had been sucked through, perhaps pushed through like removing lumps using a sieve.
He closed his eyes again and sighed. He wandered out into the corridor. There was a crowd congregating outside the door.
The Doctor subtly sonicked the door shut, and hid it in his trouser pocket.
The head of physics was white and tried to peer around him. The Doctor nodded slowly.
"Everyone go back to class," he announced, and they reluctantly dispersed. He searched the corridor for his class, but they had all obviously gone as far away as possible.
"I'm telling the Head to close the school. I didn;t imagine this."
"He won't do it. And besides, one of the children was at home when they died."
"What? This is the...why hasn't someone done something? UNIT, or Torchwood or..."
"He's scared. Scared they think it was us. That we were perverts or something."
"How many?"
"Six."
"SIX? What are you doing? Telling people they've been expelled?"
He looked ashamed, and nodded.
"I WAS BEING...what about the parents?" The Doctor held his hands out and breathed out heavily, to calm himself.
"They share the Head's views, so far..."
"Or, they've been made to. This has to stop. Now. That, was an indiscriminate vicious alien force, and it's targeting humans- in what pattern, I don't have time to find out. George, are you going to help me or not?"
"You're not a teacher, are you?"
He reached out and removed the Sonic screwdriver from the Doctor's pocket, and turned it slowly in his fingers.
"No. Guess what I am..."
"An alien hunter?"
"Close enough. Yes or no. People have been murdered!"
"Yes. For the children."
"For the children."