Somehow the paintbrush had done it. What had the Doctor called it? The abstract escaping into reality. The Angel had not travelled across the bristles like static energy, but entered through the eyes. An image of an Angel is an Angel.

Clara crawled backwards across the cold marble floor of the gallery, away from the Angel as quickly as possible, when her hand touched stone. It was the Doctor.

On the floor in front of her now, heaving and panting for breath, was an Angel. An actual, real-life, flesh and blood angel, with feathers for wings, with muscles and bones and a dress as if it had just stepped out of a storybook of Greek mythology. Clara clawed across the Doctor's pants, trying to get up, but there was nothing she could do. He'd been petrified. Perseus failed to defeat Medusa. His face had been sculpted into permanent surprise, because finally someone had managed to shut him up. The Doctor had been turned to stone.

He'd become a permanent addition to Michelangelo's curriculum vitae. One day, he'd make a fine exhibition in the British Museum. The Angel laughed.

"Doctor!" Clara begged. Then she blinked.

A stone finger was suddenly pressed into her lips, shushing her. His eyebrows looked even more menacing immortalized in marble.

Her eyes followed the Doctor's other hand, pointed at the Angel. Then she closed them shut.

And opened them again. The Doctor had moved. She blinked and watched him move, like a stop-motion film. Image after image, motion after motion. Slowly, the Doctor mimed his plan. In his hand, the sonic screwdriver had been carved out of the same stone as his flesh.

"A quantum lock, it's like a door, isn't it?" Clara said. "If it can be opened once, it can be opened again. All we need is a key. Sort of. I know it's not like that, but let's just say it is. So what do I do, Doctor? Is it the brush? Is it the Angel? Is it me?"

Blink. Blink. Blink. The last time, the Doctor disappeared, leaving only a handful of gravel behind.

"That's not good. Doctor!"

As the Angel got up, spreading its wings wide in triumph, it moved its hands through her black hair. Her entire body seemed covered in white chalk. Dust clouds followed whenever she moved.

Her face was round and innocent and her eyes were paler than blue. The Angel was beautiful, stunningly so, even. And she wasn't weeping. In fact, her features morphed into a snarling lion, with a mouth full of fangs. Her hands turned into claws. She shrieked and Clara had to cover her ears. The air itself seemed to have gone colder. The Angel was drawing energy from the room.

Then Clara saw the Doctor behind the Angel, frozen in a single gesture, pointing at the door.

"Yup, time to run."