Follow his double's orders

Jake hurriedly stood. The dolls clustered around his feet, stopping Jake from easily escaping. He looked in the mirror, and saw that to his horror, neither he, nor his doppelgänger had reflections. Jake could just see a cluster of dolls, with one hovering in midair. He dropped the doll he was holding, and the hovering doll also dropped to the ground.

"How did you get in here?" Jake asked his double.

"Magic", the doppelgänger replied. "How else?"

Jake stared uncomprehendingly. His double sighed.

"Mirrors have special powers", he explained. "In the right conditions, they can be windows into the soul."

"So, you're my soul?" Jake asked hesitantly.

"How would I know?" the doppelgänger retorted. "I could never get the hang of all that metaphysical stuff."

There was an awkward pause as Jake and his double stared at each other. Jake found this eerie. He had never really seen himself in three dimensions; even with mirrors and videos, Jake's mind had always interpreted them two-dimensionally. His double, though, had depth that his mirror image had never had.

"What do you want from me?" Jake finally asked.

The doppelgänger's answering grin was slightly deranged.

"I want to take your place", he said.