Latimer indulged in that peculiarly dry smile of his.  “If the Government had got hold of them I think their destination would have been a much warmer one than Siberia.  As it was they disappeared just in time.  There was a gang of them—­four or five at the least—­and all men of position and influence.  They must have made an enormous amount of money out of the Japs.  In the end one of them rounded on the others—­at least that’s what appears to have happened.  Anyhow McMurtrie and Savaroff skipped, and skipped in such a hurry that they seem to have left most of their savings behind them.  I suppose that’s what made them start business again in England.”

“You’re absolutely sure they’re the same pair?” asked Tommy.

“Absolutely.  I’ve got their full description from the Russian police.  It tallies in every way—­even to Savaroff’s daughter.  There is a girl with them, I believe?”

“Yes,” I said.  “There’s a girl.”  Then I paused for a moment.  “Look here, Latimer,” I went on.  “What is it you want me to do?  I’ll help you in any way I can.  When I made my bargain with McMurtrie I hadn’t a notion what his real game was.  I don’t in the least want to buy my freedom by selling England to Germany.  The only thing I flatly and utterly refuse to do is to serve out the rest of my sentence.  If it’s bound to come out who I am, you must give me your word I shall have a reasonable warning.  I don’t much mind dying—­especially if I can arrange for ten minutes with George first—­but quite candidly I’d see England wiped off the map before I’d go back to Dartmoor.”

Latimer made a slight gesture with his hands.  “You’ve saved my life, once at all events,” he said.  “It may seem a trifle to you, but it’s a matter of quite considerable importance to me.  I don’t think you need worry about going back to Dartmoor—­not as long as the Secret Service is in existence.”

“Well, what is it you want me to do?” I asked again.

He was silent for a moment or two, as though arranging his ideas.  Then he began to speak very slowly and deliberately.

“I want you to go on as if nothing had happened.  Write to McMurtrie the first thing tomorrow morning and tell him that you’ve made the powder.  He is sure to come down to the hut at once.  You can show him that it’s genuine, but on no account let him have any of it to take away.  Tell him that you will only hand over the secret on receipt of a written agreement, and make him see that you’re absolutely serious.  Meanwhile let me know everything that happens as soon as you possibly can.  Telegraph to me at 145 Jermyn Street.  You can send in the messages to Tilbury by the man who’s looking after your boat.  Use some quick simple cypher—­suppose we say the alphabet backwards, Z for A and so on.  Have you got plenty of money?”

I nodded.  “I should like to have some sort of notion what you’re going to do,” I said.  “It would be much more inspiriting than working in the dark.”