“To find out who the person was that your cousin gave this particular print to!” said Chettle eagerly.  “Of course, it’s a big field.  So far as I understand things, he’d been knocking round a good bit between the time of your taking this photo and his death.  He’d been in London, hadn’t he?  And in Russia—­in two or three places.  How can we find out when and how he parted with this?  For give it to somebody he did, and that somebody was a person who knew of the jewel transaction, and employed Lydenberg in it, and sent the photo to Lydenberg so that he should know your cousin by sight—­at once.  Mr. Allerdyke, the secret of these murders and thefts is—­there!”

Chettle replaced the watch in the cardboard box from which he had taken it, produced a bit of sealing-wax from his pocket, sealed up the box, and put it and the other things belonging to Lydenberg back in the small trunk from which he had withdrawn them to show his companion.  And Allerdyke watched him in silence, wondering and speculating about this new development.

“What do you want me to do?” he asked suddenly.  “You’ve got some scheme, of course, or you wouldn’t have got me down here alone.”

“Just so,” agreed Chettle.  “I have a scheme—­and that’s why I did get you down here alone.  Mr. Allerdyke, you’re a sharp, shrewd man—­all you Yorkshiremen are!—­at least, all that I’ve ever come across.  You’re good hands at ferreting things out.  Now, Mr. Allerdyke, let’s be plain—­there’s no two ways about it, no doubt whatever of it, the only people in England that we’re aware of who knew about this Nastirsevitch jewel transaction are—­Fullaway and whoever he has in his employ!  We know of nobody else—­unless, indeed, it’s the Chicago millionaire, Delkin, and he’s not very likely to have wanted to go in for a job of this sort.  No, sir—­Fullaway is the suspected person, in my opinion!—­though I’m going to take precious good care to keep that opinion to myself yet awhile, I can tell you.  Fullaway, Mr. Allerdyke, Fullaway!”

“Well?” demanded Allerdyke.  “And so—­”

“And so I want you to use your utmost ingenuity to find out if your cousin James gave that photo to Fullaway,” continued Chettle.  “We know very well that he was in touch with Fullaway before he went off to Russia—­I have it in my notes that when Fullaway came to see you here in Hull, at the Station Hotel, the day of your cousin’s death, he told you that he and Mr. James Allerdyke had been doing business for a couple of years, and that they’d last met in London about the end of March, just before your cousin set off on his journey to Russia.  Is that correct?”

“Quite correct—­to the letter,” answered Allerdyke.

“Very well,” said Chettle.  “Now, according to you, that ’ud be not so very long after you took that snapshot of your cousin?  So, he’d probably have the third print of it—­the one we’ve just been looking at—­on him when he was in London at that time?”