The students sat in silent awe at the Doctor, as he looked at them expectantly, not sure why they weren't saying anything.

"Doctor, where are we… Huh?" said Amy, as she and Rory step out of the TARDIS. They look at the room, a bit shocked.

"School?" asks Rory, "I thought we were done with that, years ago." He whines.

Resuming his position of authority, Will steps forward. "Hello, I'm Will Schuester. This is the, uh, the McKinly High School Glee Club."

"Hello there, Will," says Amy, who is silenced with a sharp shove from Rory.

"Now, will you explain to us what is going on please?" This remark came from Mercades, who stood next to Tina, crying on the floor.

"Yes!" said the Doctor, stepping further into the room. "We're looking for someone. And Someone is looking for Someone Else… But if Someone finds Someone Else, Anyone could be Someone, and Everyone could be Someone Else."

"Excuse me," said Santana, "But you're just talking crap now."

"No I'm not, I –" his voice was cut off, by the sound of something rumbling through the ceiling. The broken ceiling began to glow with a reddish light, and the Doctor said, "Oh no… She's here."

"Who is here, Doctor?" asked Amy, running up to him.

The Doctor was still talking rubbish. "I'd hoped to get here later, make her easier to catch, and less dangerous for…" his voice trailed off.

Amy spoke again. "What's going on?"

The Doctor sighed, and placed his hands on Amy's shoulders. "Long ago, there was a woman called Cassandra. She was obsessed with her own personal survival, to the point that she learned how to strip her soul out of her body in order to inhabit younger, healthier humans."

"So what does this have to do with her?" asked Rory, protectively moving closer to his wife.

"She died. But, somehow, before she died, she managed to make a Secondary Consciousness Converter."

Amy was confused. "A what?"

"It's basically a copy of her soul. Only it has no body. At the moment, it's just brainwaves flying around. But it needs a body to live in."

"So why doesn't it just get a dead corpse or something? Like a zombie." asked Rory.

"Cassandra is… picky. She only wants good-looking people, really. Which is why Amy is in trouble."

Amy, more scared of Cassandra than flattered by the Doctor, took a step back and looked at the ceiling.

"Oh, my God!" cried Rory, turning to the Doctor. "Will I be safe?"

"You," replied the Doctor, "Have nothing to worry about."

However, Rory didn't have time to reply, when the red light descended from the ceiling. The Glee kids, who had been listening intently, stared, terrified, at the red light.

"Cassandra…" called Amy, when the Doctor stopped her.

"It's just a soul, no voice. Yet." The light began to grow and swell. "Amy, hide!" the Doctor shoved her backwards, just as the light grew unbearably bright. Everyone in the room squinted their eyes, as red light blinded them all.

Then, at last, the light dimmed. It shrank, and fizzled out, and the room was plunged into dull light all over again.

"Doctor…" said Rory, "It's gone. Cassandra's gone."

"Not gone, Rory," he said, inspecting everyone in the room very closely, "She's moved. She inside one of us right now… The trouble is, which one?"

They looked back and forth, not sure who to be afraid of, or who to suspect. But one of them was completely calm, for Cassandra had found her new body. And nobody knew who.