’You’ve got to go straight off to the Kyle and not waste any time on the way.  Nobody suspects you, so you can travel any road you please.  When you get there you ask for Mr Andrew Amos, who has some Government job in the neighbourhood.  Give him that paper from me.  He’ll know what to do with it all right.  Tell him I’ll get somehow to the Kyle before midday the day after tomorrow.  I must cover my tracks a bit, so I can’t come with you, and I want that thing in his hands just as fast as your legs will take you.  If anyone tries to steal it from you, for God’s sake eat it.  You can see for yourself that it’s devilish important.’

‘I shall be back in England in three days,’ he said.  ’Any message for your other friends?’

’Forget all about me.  You never saw me here.  I’m still Brand, the amiable colonial studying social movements.  If you meet Ivery, say you heard of me on the Clyde, deep in sedition.  But if you see Miss Lamington you can tell her I’m past the Hill Difficulty.  I’m coming back as soon as God will let me, and I’m going to drop right into the Biggleswick push.  Only this time I’ll be a little more advanced in my views . . .  You needn’t get cross.  I’m not saying anything against your principles.  The main point is that we both hate dirty treason.’

He put the case in his waistcoat pocket.  ‘I’ll go round Garsbheinn,’ he said, ’and over by Camasunary.  I’ll be at the Kyle long before evening.  I meant anyhow to sleep at Broadford tonight . . .  Goodbye, Brand, for I’ve forgotten your proper name.  You’re not a bad fellow, but you’ve landed me in melodrama for the first time in my sober existence.  I have a grudge against you for mixing up the Coolin with a shilling shocker.  You’ve spoiled their sanctity.’

‘You’ve the wrong notion of romance,’ I said.  ’Why, man, last night for an hour you were in the front line—­the place where the enemy forces touch our own.  You were over the top—­you were in No-man’s-land.’

He laughed.  ‘That is one way to look at it’; and then he stalked off and I watched his lean figure till it was round the turn of the hill.

All that morning I smoked peacefully by the burn, and let my thoughts wander over the whole business.  I had got precisely what Blenkiron wanted, a post office for the enemy.  It would need careful handling, but I could see the juiciest lies passing that way to the Grosses Haupiquartier.  Yet I had an ugly feeling at the back of my head that it had been all too easy, and that Ivery was not the man to be duped in this way for long.  That set me thinking about the queer talk on the crevice.  The poetry stuff I dismissed as the ordinary password, probably changed every time.  But who were Chelius and Bommaerts, and what in the name of goodness were the Wild Birds and the Cage Birds?  Twice in the past three years I had had two such riddles to solve—­Scudder’s scribble in his pocket-book, and Harry Bullivant’s three words.  I remembered how it had only been by constant chewing at them that I had got a sort of meaning, and I wondered if fate would some day expound this puzzle also.