“Such seems to have been the case. How much did you owe him?”

“Owe him! Hume, you seem disposed to ask some very odd questions.”

“You think so? When a person is suspected of a crime, the first thing one looks for is a motive; you understand?”

“I understand your bare words, but what is behind your bare words I do not understand.”

“Presently you will. Before we part I will endeavour to make myself sufficiently plain. I repeat my question: How much did you owe him?”

“Nothing.”

“You lie.”

“Hume, that is the second time you have used such language to me this morning, and the second time I have refrained from knocking you down.”

“That is true. Perhaps my turn will come to be knocked down. I am aware that you are the sort of person who, for less cause, will do much more than knock a man down.” He inclined his head further towards me, his resemblance to a bird of prey becoming still more pronounced. “Ferguson, I’m a pathologist; a student of mental diseases. As such I have regarded you for some time with growing interest. Unless I err you are the victim of a form of aberration which is not so unusual as some may suppose; you suffer from mnemonic intervals.”

“I have not the faintest notion what you mean.”