“Exactly—­exactly!” broke in Fullaway.  “The very thing!  Well—­you understand, Allerdyke.  Van Koon and I will want to keep our operations to ourselves.  We don’t want police interference.  So, if any of these Scotland Yard chaps come to you here for talk or information, don’t bring me into it.  And don’t expect me to tell what we’re doing until we’ve carried out our investigations.  No interim reports, you know, Allerdyke.  Personally, I believe we’re on the track.”

“Do just what you please,” replied Allerdyke.  “You’re not the only two who are after that reward.  Go ahead—­your own way.”

He turned into the restaurant and ordered his lunch, and while it was being brought sat drumming his fingers on the table, staring vacantly at the people about him and wondering over the events of the morning.  Rayner’s, or Ramsay’s, vague hint that something might suddenly clear everything up; Fullaway’s announcement that he and Van Koon had put their heads together; Mrs. Perrigo’s story of the French maid and the young man who led blue-ribboned pug-dogs—­but all these were as nothing compared to the fact that Mrs. Marlow had actually shown him the photograph which he had until then firmly believed to lie hidden in the case of Lydenberg’s watch.  That beat him.

“Is my blessed memory going wrong?” he said to himself.  “Did I actually print more than four copies of that thing!  No—­no!—­I’m shot if I did.  My memory never fails.  I did not print off more than four.  James had three; I had one.  Mine’s in my album upstairs.  I know what James did with his.  Cousin Grace has one; Wilson Firth has another; he gave the third to this Mrs. Marlow—­and she’s got it!  Then—­how the devil did that photograph, which looks to be of my taking, which I’d swear is of my taking, come to be in Lydenberg’s watch?  Gad—­it’s enough to make a man’s brain turn to pap!”

He was moodily finishing his lunch when Chettle came in to find him.  Allerdyke, who was in a quiet corner, beckoned the detective to a seat, and offered him a drink.

“Well?” he asked.  “What’s been done?”

“It’s all right,” answered Chettle.  “I’ve told no more than was necessary—­just what we agreed upon.  To tell you the truth, our folks don’t attach such tremendous importance to it—­they will, of course, when you tell them your story about the photo.  Just at present they merely see the obvious fact—­that Lydenberg was furnished with the photo as a means of ready identification of your brother.  No—­at this moment they’re full of the Perrigo woman’s story—­they think that’s a sure clue—­a good beginning.  Somebody, they say, must own, or have owned, those pugs!  Therefore they’re going strong on that.  Meanwhile, I’m going back to Hull for at any rate a few days.”

“You’ve still got that watch on you?” asked Allerdyke.

“Certainly,” answered Chettle, clapping his hand to his breast-pocket.  “Technically speaking, it’s in charge of the Hull police—­it’ll have to be produced there.  Did you want to see it again, Mr. Allerdyke?”