stroked his moustache thoughtfully. "And to think, too," he went on
with a somewhat sheepish air, "we should have had those photographs
there in our power all those days and nights, and have let them in
the end slip like that through our fingers! To think he should have
found it out sooner than we! To think that an amateur like the
murderer should have outwitted us!"

"But how do you know," I cried, "there was ever more than one
photograph? How do you know this wasn't the only negative?"

"Because," the Inspector answered quickly, pointing to a figure in
the corner of the proof, "do you see that six? Well, that tells the
tale. Each plate of the series was numbered so in the apparatus.
Number six could only fall into focus after numbers one, and two,
and three, and four, and five, had first been photographed. We've
only got the last--and least useful for our purpose. There must have
been five earlier ones, showing every stage of the crime, if only
we'd known it."

I was worked up now to a strange pitch of excitement.

"And how did this one come into your possession?" I asked, all
breathless. "If you managed to lay your hands on one, why not on all
six of them?"

The Inspector drew a long breath.

"Ah, that's the trouble!" he replied, still gazing at me hard. "You
see, it was this way. As soon as we found the camera was missing, we
came to the conclusion the murderer must have returned to The Grange