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sealed up the box, and put it and the other things belonging to Lydenberg back in the small trunk from which he had withdrawn them to show his companion.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.