plan would be checkmated before it could be tried.  Blenkiron said that there was no evidence that a single brain was behind it all, for there was no similarity in the cases, but he had a strong impression all the time that it was the work of one man.  We managed to close some of the bolt-holes, but we couldn’t put our hands near the big ones.  ’By this time,’ said he, ’I reckoned I was about ready to change my methods.  I had been working by what the highbrows call induction, trying to argue up from the deeds to the doer.  Now I tried a new lay, which was to calculate down from the doer to the deeds.  They call it deduction.  I opined that somewhere in this island was a gentleman whom we will call Mr X, and that, pursuing the line of business he did, he must have certain characteristics.  I considered very carefully just what sort of personage he must be.  I had noticed that his device was apparently the Double Bluff.  That is to say, when he had two courses open to him, A and B, he pretended he was going to take B, and so got us guessing that he would try A. Then he took B after all.  So I reckoned that his camouflage must correspond to this little idiosyncrasy.  Being a Boche agent, he wouldn’t pretend to be a hearty patriot, an honest old blood-and-bones Tory.  That would be only the Single Bluff.  I considered that he would be a pacifist, cunning enough just to keep inside the law, but with the eyes of the police on him.  He would write books which would not be allowed to be exported.  He would get himself disliked in the popular papers, but all the mugwumps would admire his moral courage.  I drew a mighty fine picture to myself of just the man I expected to find.  Then I started out to look for him.’

Blenkiron’s face took on the air of a disappointed child.  ’It was no good.  I kept barking up the wrong tree and wore myself out playing the sleuth on white-souled innocents.’

‘But you’ve found him all right,’ I cried, a sudden suspicion leaping into my brain.

‘He’s found,’ he said sadly, ’but the credit does not belong to John S. Blenkiron.  That child merely muddied the pond.  The big fish was left for a young lady to hook.’

‘I know,’ I cried excitedly.  ‘Her name is Miss Mary Lamington.’

He shook a disapproving head.  ’You’ve guessed right, my son, but you’ve forgotten your manners.  This is a rough business and we won’t bring in the name of a gently reared and pure-minded young girl.  If we speak to her at all we call her by a pet name out of the Pilgrim’s Progress . . .  Anyhow she hooked the fish, though he isn’t landed.  D’you see any light?’

‘Ivery,’ I gasped.

’Yes.  Ivery.  Nothing much to look at, you say.  A common, middle-aged, pie-faced, golf-playing high-brow, that you wouldn’t keep out of a Sunday school.  A touch of the drummer, too, to show he has no dealings with your effete aristocracy.  A languishing silver-tongue that adores the sound of his own voice.  As mild, you’d say, as curds and cream.’