“You have that one sheet?” Jesson asked eagerly.

Nigel produced it from his pocketbook, smoothed it cut, and laid it upon the table.

“There are two things worth noticing here,” he pointed out.  “The first is that the actual name of a town in Russia is given, and a telephone number in London.  Kroten I have looked up on the map.  It seems to be an unimportant place in a very desolate region.  The telephone number is Oscar Immelan’s.”

“That is interesting, though not surprising,” Jesson declared.  “Immelan, as you of course know, is one of your enemies, one of those who are working in this country for purposes of his own.  But as regards Kroten, may I ask where you obtained your information about the place?”

Nigel dragged down the atlas and showed them the paragraph.  Jesson read it with a faint smile upon his lips.

“I fancy,” he remarked, “that this is a little out of date.  I should like, if you have no objection, to start for Kroten this week.”

“Good heavens!  Why?” Nigel exclaimed.

“I can scarcely answer that question,” Jesson said.  “I am like a man with a puzzle board and a heap of loose pieces.  Kroten is one of those pieces, but I haven’t commenced the fitting-in process yet.  Here,” he said, “is as much as I can tell you about it.  There are three cities, situated in different countries in the world, which are each in their way connected with the danger which is brewing for this country.  I have heard them described as the three secret cities.  One is in Germany.  I have been there at the risk of my life, and I came away simply puzzled.  Kroten is the next, and of the third I have still to discover the whereabouts.  Are you willing, Lord Dorminster, to let me act for you abroad?  I require no salary or remuneration of any sort.  I am a wealthy man, and investigations of this kind are my one hobby.  I shall not move without your permission, although I recognise, of course, that your own position is entirely an unofficial one.  If you will trust me, however, I promise that all my energies shall be devoted to the interests of this country.”

Nigel held out his hand.

“It is a pact,” he decided.  “Before you leave, I will give you the whole of my uncle’s brief correspondence with Sidwell.  You may be able to gather from it what he was after.  Sidwell, you remember, was stabbed in a cafe in the slums of Petrograd.”

“I remember quite well,” Jesson admitted quietly.  “I knew Sidwell.  He was a clever person in his way, but he relied too much upon disguises.  I fancy that I hear the voices of the ladies coming.  I shall just have time to tell you rather a curious coincidence.”

The two men waited eagerly.  Jesson touched with his forefinger the sheet of paper which he had been studying.

“Sidwell,” he concluded, “could not have been so far off the mark.  The man with whom he was spending the evening in that cafe was a mechanic from Kroten.”