“Hmm.” The man smiled, showing his calcium stain. “And what did I say before in German?”

“ ‘Only the dose insures the thing will not be a poison.’ ”

“Correct!” snapped the bookseller. “And in reference to education you may already have had too much-at least of a certain kind.”

“I hardly ever go to school,” Lloyd corrected. “But I am quick.”

“Perhaps,” the man said, flexing his hump. “But you are slow to leave. I believe you were sent by one of the local dilettantes to goad and annoy me.”

“I wasn’t sent by anyone!” Lloyd insisted. “I’m here on my own.”

There was something about the emphatic way the boy uttered this last remark, combined with his unexpected erudition, that made the bookseller change his attitude, for he brushed some of the dust from his suit and said, “All right, my learned young friend. Since you are so committed, you may remain here and read. I close at four, and you are not to wander outside this room. Understood?”

“Thank you!” Lloyd beamed. “Thank you. But… is there any key to how the books are organized?”

The humped man stroked his mustache.

“The key is right here,” he said, pointing to his shining forehead. “I know where every book is in the entire shop. Does my young sir have special interests?”

“I am interested in science. And magic,” Lloyd answered. “And… secrets.”

“I… see,” the bookseller said, arching his woolly eyebrows.

The humped man disappeared into the next room and Lloyd heard him foraging among the piles. He returned with an armload of Euclid’s Elements and a book concerning Hooke’s microscopy and an alchemical folio titled “Tract on the Tincture and Oil of Antimony,” by Roger Bacon.

“Feast your mind on these. But mark what I say about staying in this room.”

So saying, the man spun around and retreated back into the gloom of maps and tomes, taking the delicate astringency of the witch hazel with him.