was coming to that. She is a clever woman. When Grell got in touch
with her the following day she may have had many reasons for assisting
him. She most likely had a shrewd idea of the situation and resolved to
profit by it to avert suspicion. While Grell was suspected she would be
safe. But it may have occurred to her that if we laid our hands on him
and he told us anything, we might get on her track. Suppose that to be
so, it is not difficult to see why she should take a prominent part in
assisting him. She would still have a certain amount of money, for he
paid her to come to England, and she, as we know, would stand at
nothing."

"It all sounds very interesting," commented the Assistant Commissioner,
"but it looks to me as though it may be a tough proposition to get
evidence bearing it out."

Foyle pulled out his watch. "My idea may all tumble to pieces as soon as
a test is applied. I can't pretend to be infallible. But we can try. I
am going back to Scotland Yard now, sir. It is ten o'clock. I expect to
be at it all night. Are you coming back?"

"No, I don't think I can be of any assistance to you. I shall be glad if
your theory does come out all right this time. The alternative
suspicions are horrible. Good night, Mr. Foyle."

CHAPTER LIII

With his mind revolving the strength and weakness of his theory, Heldon
Foyle returned to Scotland Yard. He paused for a moment at the door of
the night-inspector's room.

"Anything for me, Slack?" he asked. "Has Mr. Bolt come in? Ah, there you
are, Bolt. Come down to my room." He led the way down the green
corridor, the divisional inspector following.

"Well?" asked the superintendent sharply, as he seated himself in his
office.

"I have seen the manager, a hall-porter and a chamber-maid at the
Palatial, sir. They repeat what they said in their statements before.
The Princess left the hotel at about ten o'clock. No one can fix the
time precisely, but it was certainly not before ten. She made up her
mind very suddenly, the manager tells me."

Foyle was rummaging with some papers. "Thanks very much, Bolt. Stand by
in case I want you. Tell Slack if he hears from Mr. Green to ask him to
leave things and come up to me."

He concentrated himself on the neat bundle of documents in front of him,
and gave his mind with complete detachment to the study of several of
them. The investigation had narrowed itself. Whoever was guilty was in
his hands. The choice lay betw