The Inspector jumped at those words like a cat upon a mouse.

"Quite right," he cried briskly, as one who at last, after long
search, finds a hopeful clue where all seemed hopeless. "It had to
do with the flash. The flash produced it. This is a photograph taken
by your father's process.... Of course you recollect your father's
process?"

He eyed me close. The words, as he spoke them, seemed to call up
dimly some faint memory of my pre-natal days--of my First State, as
I had learned from the doctors to call it. But his scrutiny made me
shrink. I shut my eyes and looked back.

"I think," I said slowly, rummaging my memory half in vain, "I
remember something about it. It had something to do with
photography, hadn't it?...No, no, with the electric light....I
can't exactly remember which. Will you tell me all about it?"

He leaned back in his chair, and, eyeing me all the time with that
same watchful glance, began to describe to me in some detail an
apparatus which he said my father had devised, for taking
instantaneous photographs by the electric light, with a clockwork
mechanism. It was an apparatus that let sensitive-plates revolve one
after another opposite the lens of a camera; and as each was
exposed, the clockwork that moved it produced an electric spark, so
as to represent such a series of effects as the successive positions
of a horse in trotting. My father, it seemed, was of a scientific
turn, and had just perfected this new automatic machine before his
sudden death. I listened with breathless interest; for up to that