favourite collie grown old, rheumatic--yes, I remember."

"Well, the experiment failed."

"The collie wasn't killed by the poison?"

"No, not by the poison, Mr. Stafford."

"So your theory didn't work except on paper."

"I think it worked, but not with the collie."

There was a pause, while Stafford looked composedly at his visitor, and
then he said: "Why didn't it work with the collie?"

"It never had its chance."

"Some mistake, some hitch?"

"No mistake, no hitch; but the wrong needle."

"The wrong needle! I should not say that carelessness was a habit with
you." Stafford's voice was civil and sympathetic.

"Confidence breeds carelessness," was Mr. Mappin's enigmatical retort.

"You were over-confident then?"

"Quite clearly so. I thought that Glencader was beyond reproach."

There was a slight pause, and then Stafford, flicking away some
cigarette ashes, continued the catechism. "What particular form of
reproach do you apply to Glencader?"

"Thieving."

"That sounds reprehensible--and rude."

"If you were not beyond reproach, it would be rude, Mr. Stafford."

Stafford chafed at the rather superior air of the expert, whose habit
of bedside authority was apt to creep into his social conversation;
but, while he longed to give him a shrewd thrust, he forbore. It was
hard to tell how much he might have to do to prevent the man from
making mischief. The compliment had been smug, and smugness irritated
Stafford.

"Well, thanks for your testimonial," he said, presently, and then he
determined to cut short the tardy revelation, and prick the bubble of
mystery which the great man was so slowly blowing.

"I take it that you think some one at Glencader stole your needle, and
so saved your collie's life," he said.

"That is what I mean," responded Mr. Mappin, a little discomposed that
his elaborate synthesis should be so sharply brought to an end.

There was almost a grisly raillery in Stafford's reply. "Now, the
collie--were you sufficiently a fatalist to let him live, or did you
prepare another needle, or do it in the humdrum way?"

"I let the collie live."

"Hoping to find the needle again?" asked Stafford, with a smile.

"Perhaps to hear of it again."

"Hello, that is rather startling! And you have done so?

"I think so. Yes, I may say that."

"Now how do you suppose you lost that needle?"

"It was taken from my pocket-case, and another substituted.

"Returning good for evil. Could you