I realized, of course, that these films might very well be an old roll belonging to Sir Eustace Pedler which had rolled in here and had not been found when the cupboard was emptied. But I did not think so. The red paper was far too fresh-looking. It was just as dusty as it would have been had it laid there for two or three days⁠—that is to say, since the murder. Had it been there for any length of time, it would have been thickly coated.

Who had dropped it? The woman or the man? I remembered that the contents of her handbag had appeared to be intact. If it had been jerked open in the struggle and the roll of films had fallen out, surely some of the loose money would have been scattered about also? No, it was not the woman who had dropped the films.

I sniffed suddenly and suspiciously. Was the smell of moth balls becoming an obsession with me? I could swear that the roll of films smelt of it also? I held them under my nose. They had, as usual, a strong smell of their own, but apart from that I could clearly detect the odour I disliked so much. I soon found the cause. A minute shred of cloth had caught on a rough edge of the centre wood, and that shred was strongly impregnated with moth balls. At some time or another the films had been carried in the overcoat pocket of the man who was killed in the tube. Was it he who had dropped them here? Hardly. His movements were all accounted for.

No, it was the other man, the “doctor.” He had taken the films when he had taken the paper. It was he who had dropped them here during his struggle with the woman.

I had got my clue! I would have the roll developed, and then I would have further developments to work upon.