“What knocks a hole in the burglar theory is the fact that Sir Horace was fully dressed when he was shot,” said the inspector.  “Burglars don’t break into a house when there are lights about, especially after having been led to believe that the house was empty.”

“So you think,” said Rolfe, “that the window was forced after the murder with the object of misleading us.”

“I haven’t said so,” replied the inspector.  “All I am prepared to say is that even that was not impossible.”

“It was forced from the outside,” continued Rolfe.  “I’ve seen the marks of a jemmy on the window-sill.  If it was forced after the murder the murderer was a cool hand.”

“You can take it from me,” exclaimed Inspector Chippenfield with unexpected candour, “that he was a cool hand.  We are going to have a bit of trouble in getting to the bottom of this, Rolfe.”

“If anyone can get to the bottom of it, you can,” said Rolfe, who believed with Voltaire that speech was given us in order to enable us to conceal our thoughts.

Inspector Chippenfield was so astonished at this handsome compliment that he began to think he had underrated Rolfe’s powers of discernment.  His tone of cold official superiority immediately thawed.

“There were two shots fired,” he said, “but whether both were fired by the murderer I don’t know yet.  One of them may have been fired by Sir Horace.  Just behind you in the wall is the mark of one of the bullets.  I dug it out of the plaster yesterday and here it is.”  He produced from a waistcoat pocket a flattened bullet.  “The other is inside him at present.”  He waved his hand in the direction of the room in which the corpse lay.

“Of course you cannot say yet whether both bullets are out of the same revolver?” said Rolfe.

“Can’t tell till after the post-mortem,” said the inspector.  “And then all we can tell for certain is whether they are of the same pattern.  They might be the same size, and yet be fired out of different revolvers of the same calibre.”

“Well, it is no use theorising about what happened in this room until after the post-mortem,” said Rolfe.

“You’d better give it some thought,” suggested the inspector.  “In the meantime I want you to interview the people in the neighbourhood and ascertain whether they heard any shots.  They’ll all say they did whether they heard them or not—­you know how people persuade themselves into imagining things so as to get some sort of prominence in these crimes.  But you can sift what they tell you and preserve the grain of truth.  Try and get them to be accurate as to the time, as we want to fix the time of the crime as near as possible.  Ask Flack to tell you something about the neighbours—­he’s been in this district fifteen years, and ought to know all about them.  While you’re away I’ll go through these private papers.  I want to find out why he came back from Scotland so suddenly.  If we knew that the rest might be easy.”