“I will do anything I can. I owe this fellow no particular good-will. He has been my ruin and my downfall.”

“Here are paper and pen. Sit at this desk and write to my dictation. Direct the envelope to the address given. That is right. Now the letter:

“DEAR SIR:

“With regard to our transaction, you will no doubt have observed by now that one essential detail is missing. I have a tracing which will make it complete. This has involved me in extra trouble, however, and I must ask you for a further advance of five hundred pounds. I will not trust it to the post, nor will I take anything but gold or notes. I would come to you abroad, but it would excite remark if I left the country at present. Therefore I shall expect to meet you in the smoking-room of the Charing Cross Hotel at noon on Saturday. Remember that only English notes, or gold, will be taken.

That will do very well. I shall be very much surprised if it does not fetch our man.”

And it did! It is a matter of history - that secret history of a nation which is often so much more intimate and interesting than its public chronicles - that Oberstein, eager to complete the coup of his lifetime, came to the lure and was safely engulfed for fifteen years in a British prison. In his trunk were found the invaluable Bruce-Partington plans, which he had put up for auction in all the naval centres of Europe.

Colonel Walter died in prison towards the end of the second year of his sentence. As to Holmes, he returned refreshed to his monograph upon the Polyphonic Motets of Lassus, which has since been printed for private circulation, and is said by experts to be the last word upon the subject. Some weeks afterwards I learned incidentally that my friend spent a day at Windsor, whence he returned with a remarkably fine emerald tie-pin. When I asked him if he had bought it, he answered that it was a present from a certain gracious lady in whose interests he had once been fortunate enough to carry out a small commission. He said no more; but I fancy that I could guess at that lady’s august name, and I have little doubt that the emerald pin will forever recall to my friend’s memory the adventure of the Bruce-Partington plans.