ay or two later Von Gulden went back to his duty on the
Belgian frontier and business called me home. I packed my solitary
portmanteau and departed. When I arrived at the frontier I opened my
luggage for the Custom officer and the whole contents were turned out
without ceremony. On the bottom was a roll of paper on a stick that I
quite failed to recognise. An inquisitive Customs House officer opened it
and immediately called the lieutenant in charge. Strange to say, he
proved to be Von Gulden. He came up to me, very gravely, with the paper
in his hand.

"'May I inquire how this came amongst your luggage?' he asked.

"I could say nothing; I was dumb. For there lay the Rembrandt. The red
spots had been smudged out of the corner, but there, the picture was.

"Well, I lost my head then. I accused Von Gulden of all kinds of
disgraceful things. And he behaved like a gentleman--he made me ashamed
of myself. But he kept the picture and returned it to Littimer, and I
was ruined. Lord Littimer declined to prosecute, but he would not see me
and he would hear of no explanation. Indeed, I had none to offer. Enid
refused to see me also or reply to my letters. The story of my big
gambling debt, and its liquidation, got about. Steel, I was ruined. Some
enemy had done this thing, and from that day to this I have been a
marked man."

"But how on earth was it done?" Steel cried.

"For the present I can only make surmises," Bell replied. "Van Sneck was
a slippery dog. Of course, he had found two of those plates. He kept the
one back so as to sell the other at a fancy price. My enemy discovered
this, and Van Sneck's sudden flight was his opportunity. He could afford
to get rid of me at an apparently dear rate. He stole Littimer's
engraving--in fact, he must have done so, or I should not have it at this
moment. Then he smudged out some imaginary spots on the other and hid it
in my luggage, knowing that it would be found. Also he knew that it would
be returned to Littimer, and that the stolen plate could be laid aside
and produced at some remote date as an original find. The find has been
mine, and it will go hard if I can't get to the bottom of the mystery
now. It is strange that your mysterious trouble and mine should be bound
up so closely together, but in the end it will simplify matters, for the
very reason that we are both on the hunt for the same man."

"Which man we have got to find, Bell."

"Granted. We will bait for him as on