To my surprise and annoyance he replied that there had been no camera. All Carton’s effects had been gone over very carefully in the hopes of finding something that might throw light upon his state of mind. He was positive that there had been no photographic apparatus of any kind.

That was rather a setback to my theory. If he had no camera, why should he be carrying a roll of films?

I set out early next morning to take my precious roll to be developed. I was so fussy that I went all the way to Regent Street to the big Kodak place. I handed it in and asked for a print of each film. The man finished stacking together a heap of films packed in yellow tin cylinders for the tropics, and picked up my roll.

He looked at me.

“You’ve made a mistake, I think,” he said, smiling.

“Oh, no,” I said. “I’m sure I haven’t.”