"Miss, there's smoke outside."
Clara looked up from her marking.
"Jamie, how can you be doing your exam if you're looking out the window?"
The rest of the class continued silently with their work.
"But Miss, it's true," said Jamie. "There really is a fire or something. I can smell it."
"Nah that's just Rowan," said a boy from the back row. "He had beans for breakfast!"
The whole class erupted into laughter and poor Rowan went red with embarrassment.
"Alright, that's enough of that."
Clara set her pen down and stood up from the desk.
She would investigate for herself; firstly to settle the class down and secondly to absolve Rowan and his breakfast.
"Eyes on your own work," she said. "You have twenty minutes."
Clara stalked to the back of the classroom. She pushed the window fully open and was hit by the strong smell of burnt caramel.
She recoiled and put a hand to her mouth to stiffle a cough. The window was slammed shut and she turned back to the class.
"Everybody stay at your desks. Jamie, come away from that window."
The kid had followed her and now had his face pressed up to the glass.
"See I told you!" he said. "The school's on fire. We're all going to die!"
The classroom erupted into chaos.
But it wasn't smoke. It was steam. And great clouds of it were billowing up from the playground below.
The source; a large metal bin whose contents had been earlier tipped out a few feet away.
The steam continued to pour out steadily but as it did so, a great column of black carbon began to rise up out of it like a souffle.
A figure stepped through the vapour.
It was Courtney, wearing safety goggles and a white lab coat that was several sizes too big.
"Cooool," she said.
A second figure came into view. John Smith, the Caretaker.
"Actually, it's about three hundred degrees."
Clara had the Doctor cornered in the Caretaker's Storeroom. His only escape was to get in the TARDIS which was parked snuggly in the corner. He was certainly considering it.
"Sugar sachets," Clara said. "You emptied six hundred sugar sachets into a bin!"
"Of course not," said the Doctor. "I had the children do it."
"Sugar, taken from the staff lunch room," she said in exasperation.
Clara turned to Courtney who had been hovering nervously behind her.
"Was it your brilliant idea to give him all that sugar?" she asked.
"I didn't give it to him, Miss. He was helping me with my science assignment."
"Oh, really," said Clara, suspiciously.
"He said my experiment was rubbish," Courtney explained. "That it needed a bigger exo-something.."
"Exothermic reaction," said the Doctor.
"Yes, that!"
Clara removed the safety goggles from Courtney's head and threw them aside.
"Are you alright?" she asked, holding Courtney by the shoulders. "Did you breathe any of that stuff in?" Clara was fussing now and had a hand on Courtney's cheek.
"I'm fine."
"Are you sure?"
"Clara, it's mostly water vapour," said the Doctor.
"Mostly?" Clara's face was thunderous.
"And.. maybe a dash of sulphur dioxide gas," he said sheepishly. "You may feel a bit light-headed."
Clara was less than amused. She turned back to Courtney.
"Go to the Principal's Office," she said softly.
"But Miss-"
"Now."
Clara waited until Courtney was out the door before turning to the Doctor again.
"Doctor, what's wrong with your hand?"
"It's nothing."
Clara pushed the Doctor into the TARDIS and dragged him to the nearest bathroom.
She now held his wrist in the basin so firmly it would probably leave a mark. For a small person, she was remarkably strong. He had underestimated her. He usually did.
But the Doctor was squirming, obviously in pain, as the tap water ran over the palm of his hand.
"Clara, I think that's enough."
"Would you like your hand to melt off?" she asked. "Because that's what's going to happen if we don't flush the acid out properly."
The sulphuric acid he'd measured out for the experiment had burnt through layers of skin and now his hand was raw and bleeding.
"Hold still."
"Maybe we could do this when you're less cross," he pleaded.
"Which will be never."
"Exactly."
After a while she turned the tap off and handed him a clean towel.
He sat on the edge of the bath, exhausted and cradling his hand protectively as it dried. The bleeding was slowing but it still looked very painful.
Clara's face softened and she felt her anger melting away.
"I'm sorry, Doctor. Not a very good nurse, am I?"
"Maybe stick to teaching."
"Trying to."
A first aid box suddenly appeared on the bench.
The Doctor looked crushed. "Oh, why is she doing that? I don't need any of that!"
Clara said nothing as she inspected the box. If the TARDIS thought it necessary, then it was necessary.
She took out a tube of antiseptic cream and a sterile dressing.
Clara sat on the edge of the bath and put a fresh towel down on her lap. She patted it and the Doctor gingerly moved his hand over.
"Why do you keep doing this?" she asked lightly.
"Doing what, exactly?" He gasped as Clara squeezed the cool antiseptic onto the wound.
"This Caretaker thing."
"They gave me a brush," he said.
"The truth, Doctor."
She started unwrapping the sterile dressing. It was a good one, made of fabric with adhesive around the edge.
"The truth is.." He took a deep breath to get the words out. "I like being near you."
Clara gently pressed the edges of the dressing down over his hand.
He closed his fingers around hers despite the pain.
It may have just been in Clara's imagination, but she could swear the TARDIS was dimming the lights ever so slowly.