“Hill is left locked up in the flat with the girl; for Birchill, who has just trusted him implicitly in a far more important matter affecting his own liberty, has a belated sense of caution about trusting his unworthy accomplice while he is away committing the burglary.  The time goes on; the couple in the flat hear the clock strike twelve before Birchill’s returning footsteps are heard.  He enters, and immediately announces to Hill and the girl, with every symptom of strongly marked terror, that while on his burglarious mission, he has come across the dead body of Sir Horace Fewbanks—­murdered in his own house.  Mark that! he tells them freely and openly—­tells Hill—­as soon as he gets in the flat.  Allowing for possible defects in my previous reasoning against Hill’s story, admitting that an adroit prosecuting counsel may be able to buttress up some of the weak points, allowing that you may have other circumstantial evidence supporting your case, that is the fatal flaw in your chain:  because of Birchill’s statement on his return to the flat no jury in the world ought to convict him.”

“I don’t see why,” said Rolfe.

Crewe fixed his deep eyes intently on Rolfe as he replied: 

“Because, if Birchill had committed this murder, he would never have admitted immediately on his returning, least of all to Hill, anything about the dead body.”

“But he told Hill that he didn’t commit the murder,” protested Rolfe.

“But you say that he did commit the murder,” retorted the detective.  “You cannot use that piece of evidence both ways.  Your case is that this man Birchill, while visiting Riversbrook to commit a burglary which he and Hill arranged, encountered Sir Horace Fewbanks and murdered him.  I say that his admission to Hill on his return to the flat that he had come across the body of Sir Horace Fewbanks, is proof that Birchill did not commit the murder.  No murderer would make such a damning admission, least of all to a man he didn’t trust—­to a man who he believed was capable of entrapping him.  Next you have Birchill consenting to a message being sent to Scotland Yard conveying the information that Sir Horace had been murdered.  Is that the action of a guilty man?  Wouldn’t it have been more to his interest to leave the dead man’s body undiscovered in the empty house and bolt from the country?  It might have remained a week or more before being discovered.  True, he would have had to find some way of silencing Hill while he got away from the country.  He might have had to resort to the crude method of tying Hill up, gagging him, and leaving him in the flat.  But even that would have been better than to inform the police immediately of the murder and place his life at the mercy of Hill, whom he distrusted.”

“Looked at your way, I admit that there are some weak points in our case,” said Rolfe.  “But you’ll find that our Counsel will be able to answer most of them in his address to the jury.  If Birchill didn’t commit the murder, who did?  Do you deny that he went up to Riversbrook that night?”