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"It's no use," said Mr. Sherlock Holmes. "To solve this case, I must employ the microscope you purchased for me."
I started, but did not protest. Wondering if he had spoilt every childhood birthday, I fetched the box from its hiding place. Re-entering the room, I ventured, "How did you know? I took every pre-caution."
Holmes took possession of the box with a self-satisfied smile. "The man who purchased this hesitated outside the shop for over thirty minutes. As he contemplated, he smoked."
I sighed. "You knew my brand."
"My dear Watson, no one is more familiar with your ash."