her, staggered as though she
had struck me a blow. "What do you mean?"

"I mean nothing," was her cold reply. "Take it as you may, Mr. Royle,
only be warned."

"But if Digby knew that she was worthless, he would surely have made some
remark to arouse my suspicion?" I exclaimed.

"Why should he?" she queried. "A true gentleman does not usually expose a
woman's secret."

I saw her point, and my heart sank within me. Were these scandalous
allegations of hers based upon truth, or was she actuated by ill-feeling,
perhaps, indeed, of jealousy?

We walked on again slowly until we reached St. James's Palace, and passed
out into the end of Pall Mall, where it joined St. James's Street. Yet
her attitude was one of complete mystery. I was uncertain whether the
admission she had so unconsciously made regarding Phrida--that she was
Digby's worst enemy--was the actual truth or not.

One thing was plain. This Mrs. Petre was a clever, far-seeing woman of
the world, who had with great ingenuity held from me her knowledge of the
crime.

A problem was, therefore, presented to me. By what means could she be
aware of it? First, she had expected to meet Digby that evening;
secondly, the letter I had brought was written before the assassination
of the unknown girl.

How could she have obtained knowledge of the affair if it were not
premeditated and hinted at in the letter I had so faithfully delivered?

Half way up St. James's Street my companion suddenly exclaimed:

"I must be going! Would you please hail me a taxi, Mr. Royle?"

"I will--when you have answered my question," I said, with great
politeness.

"I have already replied to it," was her response. "You love Phrida Shand,
but if you have any self-respect, any regard for your future, break off
Whatever infatuation she has exercised over you. If you are Digby's
friend, you will be a man, and act as such!"

"I really don't follow you," I said, bewildered.

"Perhaps not. But surely my words are plain enough!"

"Is she the enemy of Digby, of whom you have spoken?"

"That question I am not permitted to answer."

I was silent a few seconds. Then I asked earnestly:

"Tell me openly and frankly, Mrs. Petre. Is she the person you suspect of
having committed the crime?"

She gave vent to a short dry laugh.

"Really, Mr. Royle," she exclaimed, "you put to me the most difficult
riddles. How can I possibly suspect anyone of a crime of which I know
nothing, and of which even