Suddenly one page seemed to strike his attention. He smoothed it out, pulled the blotter closer towards him, and took from his pocket photographs of the famous letters in the case.
He put one of the photographs upon a leaf of the blotter and compared them carefully. Then he took a small glass from his pocket and examined the photograph and the page of the blotter with that.
When he had, apparently, satisfied himself, he looked round with a white, stern face to where the defiant but trembling woman was standing by the fireplace.
There was a silence for a moment. It was broken by Lady Attwill saying, "Can I do anything for you?"
"Yes," Collingwood replied; "you can bring me that looking-glass from that small table there."
She looked at him without saying a word.
"You don't seem very eager," he said. "But there is an excellent mirror over the fireplace."
At that, as if hypnotised, she went up to the little table by the piano and took up a small Italian mirror framed in ivory and silver.
She gave it to him. "Well," she asked, "have you solved the mystery?"
"Wait!" he replied. He took the mirror in one hand, propping up the blotter with its back towards him, and looking intently into the glass.