As I puzzled over the subject, certain conclusions began to form in my mind.  The four identical sentences seemed to hint that ’Deep Breathing’ had Boche affiliations.  Here was a chance of communicating with the enemy which would defy the argus-eyed gentlemen who examine the mails.  What was to hinder Mr A at one end writing an advertisement with a good cipher in it, and the paper containing it getting into Germany by Holland in three days?  Herr B at the other end replied in the Frankfurter, and a few days later shrewd editors and acute Intelligence officers—­and Mr A—­were reading it in London, though only Mr A knew what it really meant.

It struck me as a bright idea, the sort of simple thing that doesn’t occur to clever people, and very rarely to the Boche.  I wished I was not in the middle of a battle, for I would have had a try at investigating the cipher myself.  I wrote a long letter to Macgillivray putting my case, and then went to sleep.  When I awoke I reflected that it was a pretty thin argument, and would have stopped the letter, if it hadn’t gone off early by a ration party.

* * * * *

After that things began very slowly to happen.  The first was when Hamilton, having gone to Boulogne to fetch some mess-stores, returned with the startling news that he had seen Gresson.  He had not heard his name, but described him dramatically to me as the wee red-headed devil that kicked Ecky Brockie’s knee yon time in Glesca, sirr,’ I recognized the description.

Gresson, it appeared, was joy-riding.  He was with a party of Labour delegates who had been met by two officers and carried off in chars-a-bancs.  Hamilton reported from inquiries among his friends that this kind of visitor came weekly.  I thought it a very sensible notion on the Government’s part, but I wondered how Gresson had been selected.  I had hoped that Macgillivray had weeks ago made a long arm and quodded him.  Perhaps they had too little evidence to hang him, but he was the blackest sort of suspect and should have been interned.

A week later I had occasion to be at G.H.Q. on business connected with my new division.  My friends in the Intelligence allowed me to use the direct line to London, and I called up Macgillivray.  For ten minutes I had an exciting talk, for I had had no news from that quarter since I left England.  I heard that the Portuguese Jew had escaped—­had vanished from his native heather when they went to get him.  They had identified him as a German professor of Celtic languages, who had held a chair in a Welsh college—­a dangerous fellow, for he was an upright, high-minded, raging fanatic.  Against Gresson they had no evidence at all, but he was kept under strict observation.  When I asked about his crossing to France, Macgillivray replied that that was part of their scheme.  I inquired if the visit had given them any clues, but I never got an answer, for the line had to be cleared at that