“You have worked it out very ingeniously,” said Walters.  “You must find the work of crime detection very fascinating.  I am afraid that if I had been in your place—­that is if I had known as much about the tragedy as you do—­when Kemp was in the witness-box yesterday, I would not have seen anything more in his evidence than the fact that he was committing perjury in order to help Holymead.”

“I think you would,” said Crewe.  “These discoveries come to one naturally as the result of training one’s mind in a particular direction.”

“They come to you, but they wouldn’t come to me,” said Walters with a smile.  “But do you think Kemp’s story of how Sir Horace was shot is literally true?  Do you think Sir Horace got in the first shot and then tried to fire again?  If that is so, I don’t see how they can hope to convict Kemp of murder—­a jury would not go beyond a verdict of manslaughter in such a case.”

“You handled Kemp so well that he was too excited to tell anything but the truth,” said Crewe.  “Sir Horace fired first and missed—­the bullet which Chippenfield removed from the wall of the library shows that—­and he pulled the trigger again but the cartridge which had been in the revolver for a considerable time, probably for years, missed fire.  Here is a silent witness to the truth of that part of Kemp’s story.”

Crewe produced from a waistcoat pocket one of the four cartridges he had removed from the revolver Mademoiselle Chiron had handed to him and he placed it on the table.  On the cap of the cartridge was a mark where the hammer had struck without exploding the powder.