The detective instantly
smiled with great unconcern. "Go on," said he, "what else did you hear?"

"Nothing else. In the mood in which I was this very plain intimation
that Miss Dare had sought my aunt, had pleaded with her for me and
failed, struck me as sufficient. I did not wait to hear more, but
hurried away in a state of passion that was little short of frenzy. To
leave the place and return to my work was now my one wish. When I found,
then, that by running I might catch the train at Monteith, I ran, and so
unconsciously laid myself open to suspicion."

"I see," murmured the detective; "I see."

"Not that I suspected any evil then," pursued Mr. Mansell, earnestly. "I
was only conscious of disappointment and a desire to escape from my own
thoughts. It was not till next day----"

"Yes--yes," interrupted Mr. Gryce, abstractedly, "but your aunt's words!
She said: 'You think you are going to marry him, Imogene Dare; but you
never shall, not while I live.' Yet Imogene Dare was not there. Let us
solve that problem."

"You think you can?"

"I think I must."

"How? how?"

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 sho