"The TARDIS. It's bigger on the inside than the outside, or did you not notice?" the Doctor asked as he floated up the steps to the gallery.
Maebh (Pronounced Mave, Gaelic in origin) followed him, surprising the Doctor with her lack of surprise. The Doctor picked up a map of London streets and it unfolded in his hands.
"I just thought it was supposed to be bigger on the inside, so I didn't say anything," Maebh said.
The Doctor drifted between the trees near their leaves, scanning with the sonic screwdriver while Maebh watched the news on her phone. The Doctor looked at the sonic screwdriver with confusion. "Why would there be no reading? Because they are actually made of wood. No circuits. No mechanism. Wood." He floated down to the ground by Maebh and one of Landseer's bronze lions.
"You can't create an overnight forest with extra special fertilizer. You have to mess with the fabric of time. And communicate with trees," the Doctor said mostly to himself as he began to understand. With a thought he was in the air and a wave of his arms sent him rushing into the TARDIS.
Clara, Danny, and the schoolchildren followed.
"So you're saying it's an act of aggression?" Clara asked.
"By trees?" the Doctor questioned.
"Er, trees clean the air," Ruby pointed out.
"Exactly. Well done, Ruby," Clara said, "Someone or something who's trying to scrub the atmosphere before colonizing or invading. Ah, yes, Doctor. Ahem. This is Coal Hill Year Eight Gifted and Talented Group."
"What are the round bits for?" Samson asked.
"Ask your teacher," the Doctor said, "Come on! Down from there! Hey!" He flew around the kids playing with the controls.
Every child he touched floated away.
"Away from the console. Come on. That's an antique. Get away from there! Don't touch that!"
They stopped touching the console and scrambled to touch the Doctor instead.
"How can you fly?"
"Can you make me fly?"
The Doctor flew straight up out of their reach. "Haven't any of you been struck by the fact that it's, look, it's bigger on the inside?" the Doctor said, trying to get their minds off him.
"There wasn't a forest. Then there was a forest. Nothing surprises us anymore," Ruby said.
"Then don't be surprised by my flying." The Doctor began to float down away from them. "These trees all appeared at once. That wasn't a coincidence. There's no such thing as an arboreal coincidence. Something, someone has coordinated this. To coordinate, you need to communicate. Every communication channel on the Tardis is open, and nothing."
Clara heard a scream in the forest. "Maebh?"
The Doctor grabbed Clara's hand and they flew, swerving between the trees. The Doctor skidded to a stop and Clara slid past him, stopping in front of a wrought iron fence. Maebh stood on the other side, a frightened and hungry pack of wolves growling behind her.
"Maebh! Doctor, fly over and get her!"
"It's all right," the Doctor said quietly.
Maebh ran along the fence.
"Maebh? Maebh!" Clara shouted. She realized Maebh had found a gate and she ran through it, quickly closing it behind her.
"Maebh. You came looking for me," the Doctor said.