Across from you sits the spitting image of yourself

For reasons beyond your comprehension, it hasn't killed and replaced you, despite the little knowledge you have of such creatures indicating that that is the usual pattern

Instead, it's just... watching you. Studying you

*It mimics your posture and mannerisms, but they're all a little off, although you doubt that anyone else could tell.

It finally opens it's mouth and speaks in your voice

What a sad life you live. I don't want it.