"But we'll discover Whitmore's movements--and without much difficulty." "How ?" Greig eyed his superior in mingled admiration and incredulity.
From the inside pocket of his coat Britz produced a photograph.
"I found this in Whitmore's house," he said.

"It is a photograph of Whitmore, a recent one.

You will observe that the mustache he wears is a heavy one.

It is much thicker than the one we saw as we examined his body to-day.

Between the time he had this photograph taken and his return to his business, he must have had the mustache shaved off.