en to this. The test with the letters failed, because what he
said about them was true. They were not meant for him. Miss Challoner
had another lover."

"Only another? I thought there were a half-dozen, at least."

"Another whom she favoured. The letters found in her possession--not
the ones she wrote herself, but those which were written to her over the
signature O. B. were not all from the same hand. Experts have been busy
with them for a week, and their reports are unanimous. The O. B. who
wrote the threatening lines acknowledged to by Orlando Brotherson, was
not the O. B. who penned all of those love letters. The similarity in
the writing misled us at first, but once the doubt was raised by Mr.
Challoner's discovery of an allusion in one of them which pointed to
another writer than Mr. Brotherson, and experts had no difficulty in
reaching the decision I have mentioned."

"Two O. B.s! Isn't that incredible, Mr. Gryce?"

"Yes, it is incredible; but the incredible is not the impossible. The
man you've been shadowing denies that these expressive effusions of Miss
Challoner were meant for him. Let us see, then, if we can find the man
they were meant for."

"The second O. B.?"

"Yes."

Sweetwater's face instantly lit up.

"Do you mean that I--after my egregious failure--am not to be kept on
the dunce's seat? That you will give me this new job?"

"Yes. We don't know of a better man. It isn't your fault, you said it
yourself, that water couldn't be squeezed out of a millstone."

"The Superintendent--how does he feel about it?"

"He was the first one to mention you."

"And the Inspector?"

"Is glad to see us on a new tack."

A pause, during which the eager light in the young detective's eye
clouded over. Presently he remarked:

"How will the finding of another O. B. alter Mr. Brotherson's position?
He still will be the one person on the spot, known to have cherished
a grievance against the victim of this mysterious killing. To my mind,
this discovery of a more favoured rival, brings in an element of motive
which may rob our self-reliant friend of some of his complacency. We may
further, rather than destroy, our case against Brotherson by locating a
second O.B."

Mr. Gryce's eyes twinkled.

"That won't make your task any more irksome," he smiled. "The loop we
thus throw out is as likely to catch Brotherson as his rival. It all
depends upon the sort of man we find in this second O. B.; and whether,
in so