"Litmus test," I said.

Then I flicked the nail gently with one finger, and sent it rolling across the surface of my desk and toward her perfectly manicured hands.

She didn't move until a split second before the nail touched her-but then she did, a blur of motion that took her two long strides back from my desk and knocked over the chair she'd been sitting on. The nail rolled off the edge of the desk and fell to the floor with a clink.

"Iron," I said. "Cold iron. Faeries don't like it."

The expression drained from her face. One moment, there had been arrogant conceit, haughty superiority, blithe confidence. But that simply vanished, leaving her features cold and lovely and remote and empty of all emotion, of anything recognizably human.

"The bargain with my godmother has months yet to go," I said. "A year and a day, she had to leave me alone. That was the deal. If she's trying to weasel out of it, I'm going to be upset."

She regarded me in that empty silence for long moments more. It was unsettling to see a face so lovely look so wholly alien, as though something lurked behind those features that had little in common with me and did not care to make the effort to understand. That blank mask made my throat tighten, and I had to work not to let the gun in my hand shake. But then she did something that made her look even more alien, more frightening.

She smiled. A slow smile, cruel as a barbed knife. When she spoke, her voice sounded just as beautiful as it had before. But it was empty, quiet, haunting. She spoke, and it made me want to lean closer to her to hear her more clearly. "Clever," she murmured. "Yes. Not too distracted to think. Just what I need."

A cold shiver danced down my spine. "I don't want any trouble," I said. "Just go, and we can both pretend nothing happened."

"But it has," she murmured. Just the sound of her voice made the room feel colder. "You have seen through this veil. Proven your worth. How did you do it?"

"Static on the doorknob," I said. "It should have been locked. You shouldn't have been able to get in here, so you must have gone through it. And you danced around my questions rather than simply answering them."

Still smiling, she nodded. "Go on."

"You don't have a purse. Not many women go out in a three-thousand-dollar suit and no purse."

"Mmmm," she said. "Yes. You'll do perfectly, Mister Dresden."

"I don't know what you're talking about," I said. "I'm having nothing more to do with faeries."

"I don't like being called that, Mister Dresden."

"You'll get over it. Get out of my office."

"You should know, Mister Dresden, that my kind, from great to small, are bound to speak the truth."

"That hasn't slowed your ability to deceive."

Her eyes glittered, and I saw her pupils change, slipping from round mortal orbs to slow feline lengths. Cat-eyed, she regarded me, unblinking. "Yet have I spoken. I plan to gamble. And I will gamble upon you."