"This is the work of very clever and accomplished thieves who somehow
became aware of two facts. One, that your cousin was bringing with him to
England the jewels of the Princess Nastirsevitch. The other, that
Mademoiselle Zélie de Longarde carried her pearls and diamonds in an
innocent-looking rosewood box. My dear sir! you observed that I examined
that box with seeming carelessness--in reality, I was looking at it with
the eye of a trained observer. I am one of those people who, from having
knocked about the world a lot, engaging in a multifarious variety of
occupations, have picked up a queer scrap-heap of knowledge, and I will
lay you any odds you like that I am absolutely correct in affirming that
the box which I just now handed to Maggie, the chambermaid, was newly
made by a Russian cabinet-maker within the last four weeks!"

"For a purpose?" suggested Allerdyke.

"Just so--for a purpose," assented Fullaway. "That purpose being, of
course, its substitution for the real original article. You did not
handle the box which is now upstairs--it is carefully weighted, though it
is empty. I believe--nay, I am sure, it contains a sheet of lead under
its delicate lining of satin. That, of course, was to deceive
Mademoiselle. You heard her say that the jewels were in her box at
Christiania, and that she never opened the box until this evening here in
Edinburgh? Very good--between here and Christiania somebody substituted
the imitation box for the real one. Ah!--in all these great criminal
operations there is nothing like sticking to the old, well-worn,
tried-and-proved tricks of the trade!--they are like well-oiled,
well-practised machinery. And now we come back to the real, great,
anxious question--Who did it? And there, Allerdyke, we are at
present--only at present, mind!--up against a very big, blank wall."