Choice's Curse {d.m.}

'Draco let his shock slip through the dense barrier of calm he had constructed, and Snape, the bastard, had the gall to look smug. "I pride myself in being rather adept at spotting imposters, Ms. Adler, and you certainly are a snake hiding in the eagle's nest, are you not?"

'"Yes," I was forced to say, even as my stomach churned. I was, I realized. I was, and I had done a damn good job of fooling everyone, even myself.'