It was not until the evening of the following day that Harley rang me up, and:

“I want you to come round at once,” he said urgently. “The Deepbrow case is developing along lines which I confess I had anticipated, but which are dramatic nevertheless.”

Knowing that Harley did not lightly make such an assertion, I put aside the work upon which I was engaged and hurried around to Chancery Lane. I found my friend, pipe in mouth, walking up and down his smoke-laden study in a state which I knew to betoken suppressed excitement, and:

“Did Wessex find your photographer?” I asked on entering.

“Yes,” he replied. “A first-class man, as I had anticipated. As I had further anticipated he did a number of copies of the picture for the foreign gentleman—about fifty, in fact!”

“Fifty!”

“Yes! Does the significance of that fact strike you?” asked Harley, a queer smile stealing across his tanned, clean-shaven face.

“It is an extraordinary thing for even an ardent admirer to have so many reproductions done of the same picture!”

“It is! I will show you now what I found trodden into one of the footprints where the struggle took place beside the car.”

Harley produced a piece of thick silk twine.