case for the prosecution.  We proved that Birchill was in the house on a criminal errand.  What more could they expect us to prove?  They couldn’t expect us to have a man looking through the window or hiding behind the door when the murder was committed.  If we could get evidence of that kind we could do without juries.  We could hang our man first and try him afterwards.  I don’t think a verdict of acquittal from a befogged jury would do so much harm in such a case.”

“You are still convinced that Birchill did it?” said Rolfe questioningly.

“I have never wavered from that opinion,” said his superior.  “If I had, this note of Hill’s would restore my conviction in Birchill’s guilt.”

“Why, how do you make out that?” replied Rolfe blankly.

“Hill says he’s clearing out of the country because he’s frightened.  What’s he frightened of?  His own guilty conscience and the long arm of the law?  Not a bit of it!  Hill’s an innocent man.  If he had been guilty he’d never have stood the ordeal of the witness-box and the cross-examination.  Hill’s cleared out because he was frightened of Birchill.”

“Of Birchill?”

“Yes.  Didn’t Birchill tell Hill, just before he set out for Riversbrook on the night of the murder, that if Hill played him false he’d murder him?  Hill did play him false, not then, but afterwards, when he made his confession and Birchill was arrested for the murder in consequence.  When Birchill was acquitted at the trial his first thought would be to wreak vengeance on Hill.  A man with one murder on his soul would not be likely to hesitate about committing another.  Hill knew this, and fled to save his life when Birchill was acquitted.  That’s the explanation of his letter, Rolfe.”

“So that’s the way you look at it?” said Rolfe.

“Of course I do!  It’s the only way Hill’s flight can be looked at in the light of all that’s happened.  The theory dovetails in every part.  I’m more used than you to putting these things together, Rolfe.  Hill’s as innocent of the murder as you are.”

“And where do you think Hill’s gone to?”

“Certainly not out of London.  He’s too much of a Cockney for that.  Besides, he’s a man who is fond of his wife and child.  He’s hiding somewhere close at hand, and I shouldn’t wonder if the whole thing’s a plant between him and his wife.  Have you forgotten how she tried to hoodwink us before?  I’ll go to the shop to-morrow and see if I can’t frighten the truth out of her.  Meanwhile, you’d better put the Camden Town police on to watching the shop.  If he’s hiding in London he’s bound to visit his wife sooner or later, or she’ll visit him, so we ought not to have much difficulty in getting on to his tracks again.”