The detective did not answer. He was buried in profound thought. Suddenly he exclaimed:
"It is, as you say, the key-note to the tragedy. It must be solved." But the glance he dived deep into space seemed to echo that "How? how?" of the prisoner, with a gloomy persistence that promised little for an immediate answer to the enigma before them. It occurred to Mansell to offer a suggestion.
"There is but one way I can explain it," said he. "My aunt was speaking to herself. She was deaf and lived alone. Such people often indulge in soliloquizing."
The slap which Mr. Gryce gave his thigh must have made it tingle for a good half-hour.
"There," he cried, "who says extraordinary measures are not useful at times? You've hit the very explanation. Of course she was speaking to herself. She was just the woman to do it. Imogene Dare was in her thoughts, so she addressed Imogene Dare. If you had opened the door you would have seen her standing there alone, venting her thoughts into empty space."
"I wish I had," said the prisoner.
Mr. Gryce became exceedingly animated. "Well, that's settled," said he. "Imogene Dare was not there, save in Mrs. Clemmens' imagination. And now for the conclusion. She said: 'You think you are going to marry him, Imogene Dare; but you never shall, not while I live.' That shows her mind was running on you."
"It shows more than that. It shows that, if Miss Dare was not with her then, she must have been there earlier in the day. For, when I left my aunt the day before, she was in entire ignorance of my attachment to Miss Dare, and the hopes it had led to."
"Say that again," cried Gryce.
Mr. Mansell repeated himself, adding: "That would account for the ring being found on my aunt's dining-room floor——"