er my own conditions, which are these: No one but
yourself shall know that I am helping you, and you yourself will not ask
me how I help you."

Once more a puzzle. Nicol Hendry thought for a few seconds before he
replied slowly:

"Yes, Professor. As long as you do help us I don't care either why or
how, for, as I may now be quite frank with you, we certainly want help
of some sort very badly. The papers are quite right for once. Neither
here nor on the Continent have we found a single clue worth picking up.
It is humiliating, but it is true."

"Then before you go I hope I shall be able to give you some that will be
worth picking up, and keeping too," said the scientist with a faint
smile; "at any rate, I think I can put you upon certain lines of enquiry
which you will find it profitable to trace out."

Nicol Hendry was an ambitious man, and he would have given a good deal
to have known what was passing in the other's mind just then, but his
expression betrayed nothing more than interested anticipation.

"We shall be entirely grateful to you if you will, Professor," he
murmured.

"I have no doubt of that, my dear sir. Now, to begin with: I presume
that there are photographs of the persons mentioned in the newspapers
as being in the Castle of Trelitz with the Prince on the last day that
he was known to be there?"

"Certainly; we should scarcely leave a simple preliminary like that
neglected," smiled Nicol Hendry. "With the exception of the Frauelein
Hulda von Tyssen, the Princess' Lady of the Bedchamber, all have been
photographed for publication, and hers we have got through a private
source. The Chief of each of our Departments has a copy of them, and I
happen to have mine in my pocket now, if you would like to see them. The
Princess, of course, you must have seen. She is in every photographer's
window in the West End."

"Oh yes, I have seen her. Who has not? She is a singularly beautiful
woman. But I should very much like to see the others, if I may."

The Chef de Bureau looked at him sharply as he took a small square
morocco case out of his inner pocket and opened it. Going to a little
table he spread out five small unmounted photographs upon it. He put two
of them on one side, saying:

"Those, of course, you know; they are the Prince and Princess. This one
is Count Ulik von Kessner, High Chamberlain of Boravia; this, Captain
Alexis Vollmar; and this is Frauelein von Tyssen."

Franklin Marmion looked at