Directly after breakfast the doctor took us into the study and we began the morning’s labours. It happened that, in working out a series of algebraic questions, de Cartienne and I used a great deal of paper, and when the doctor looked for a piece to explain the working of a rather stiff quadratic, the rack was empty.
“Have either of you a piece of wastepaper in your pockets?” he asked. “The back of an envelope, or anything will do. I see it is lunch-time, so it is scarcely worth while sending for any.”
I felt in all my pockets, but they were empty. de Cartienne drew an envelope from his pocket and handed it to the doctor. The moment he had parted with it, however, I saw him give a sudden start and he seemed as though about to make an effort to regain possession of it. But he was too late, for the doctor was already fast covering it with figures.
de Cartienne quitted his seat and stood looking over his shoulder, probably hoping that I should do the same. But I remained where I was, taking care to manifest my interest in the problem by asking frequent questions. The moment the doctor had finished his rapid figuring and solved the equation, I stretched out my hand for it eagerly.
“May I see it, sir?” I begged. “I fancy you’ve made a mistake in the values.”
He handed it across the table at once, with a quiet smile.
“I think not, Morton,” he said. “Examine it for yourself.”
de Cartienne moved round to my side, with nervously twitching lips and an ugly light in his eyes.
“One moment, Morton,” he said. “I won’t keep it longer.”
I laid a hand upon it, and pushed him back with the other.