Allerdyke helped himself to a fresh cigar out of a box which lay on Fullaway’s table, lighted it, and smoked in silence for a minute or two.  The other men, feeling instinctively that he was thinking, waited.

“Look you here!” he exclaimed suddenly.  “Clue?  Yes, that’s what we want.  Where’s that clue likely to be found?  Why, in this, and this only—­who knew, person or persons, that my cousin was bringing those jewels from the Princess Nastirsevitch to this country?  Get to know that, and it narrows the field, d’ye see?”

“There’s the question of Miss Lennard’s jewels, too,” remarked Fullaway.

“That may be—­perhaps was—­a side-issue,” said Allerdyke.  “It may have come into the big scheme as an after-thought.  But, anyway, that’s what we want—­a first clue.  And I don’t see how that’s to be got at until this Princess arrives here.  You see, she may have talked, she may have let it out in confidence—­to somebody who abused her confidence.  What is certain is that somebody must have got to know of this proposed deal between the Princess and your man, Fullaway, and have laid plans accordingly to rob the Princess’s messenger—­my cousin James.  D’ye see, the deal was known of at two ends—­to you here, to this Princess, through James, over there, in Russia.  Now, then, where did the secret get out?  Did it get out there, or here?”

“Not here, of course!” answered Fullaway, with emphasis.  “That’s dead sure.  Over there, of a certainty.  The robbery was engineered from there.”

“Then, in that case, there’s naught to do but wait the arrival of the Princess,” said Allerdyke.  “And you say she’ll be here to-morrow night.  In the meantime no doubt you police gentlemen’ll get more news about this last affair at Hull, and perhaps Miss Lennard’ll find those references about the Frenchwoman, and maybe we shall mop things up bit by bit—­for mopped up they’ll have to be, or my name isn’t what it is!  Fullaway,” he went on, rising from his chair, “I’ll have to leave you—­yon man o’ mine’ll be arriving from Yorkshire with my things before long, and I must go down to the hotel office and make arrangements about him.  See you later—­at dinner to-night, here, eh?”

He lounged away through the outer office, giving the smart lady secretary a keen glance as he passed her and getting an equally scrutinizing, if swift, look in return.

“Clever!” mused Allerdyke as he closed the door behind him.  “Deuced clever, that young woman.  Um—­well, it’s a pretty coil, to be sure!”

He went down to the office, made full and precise arrangements about Gaffney, who was to be given a room close to his own, left some instructions as to what was to be done with him on arrival, and then, hands in pockets, strolled out into Aldwych and walked towards the Strand, his eyes bent on the ground as if he strove to find in those hard pavements some solution of all these difficulties.  And suddenly he lifted his head and muttered a few emphatic words half aloud, regardless of whoever might overhear them.