‘The door may have been shut. He may have been deaf.’

‘He’d need to be stone-deaf. Talk sense!’

‘I don’t see how anyone got in by that ventilator, sir,’ said the Sergeant, after thinking it over. ‘Looks as though he must have come in through the door after all.’

Hemingway got down from the stool, and returned to the bedroom. ‘Very well. We’ll take it that he did. For what it’s worth, the body was found lying with its back to the door.’

The Sergeant frowned. ‘Well, sir, what is it worth?’

‘Nothing at all,’ replied Hemingway. ‘You can say that someone stole into Nathaniel’s room without his knowing it, and stabbed him in the back; and you can just as easily say that he was facing the other way when he was stabbed, and staggered round before collapsing. May have been trying to get to that bell by the fireplace. I had a talk with the police-surgeon, and he tells me that a stab to the right of the spine, in the lumbar region, wouldn’t kill a man instantaneously. So the position of the body doesn’t help us much.’

‘Was the door locked before the murder, sir?’

‘Nobody knows, seeing that nobody knows when he was murdered. If I was one to let my imagination run away with me, which I’m not, I should say Nathaniel locked the door himself.’

‘Why, sir?’

‘On the evidence. You should always listen to evidence. Half the time it’s a pack of lies, but you never know. In this case, all the witnesses say that Nathaniel was in a raging temper; and Brother Joseph admits that he was trying to smooth the old boy down, and getting ticked off for his pains. Followed him half-way up the stairs, he did. Now, if you were Nathaniel in a temper, being followed about by Joseph, what would you do?’

‘I don’t rightly know,’ said the Sergeant, staring.

‘Then all I can say is you’ve taken more of a fancy to Joseph than I have. If I had a wind-bag like that on my tail, I’d lock my door, and very likely shove a heavy piece of furniture against it as well.’

The Sergeant smiled, but ventured to say: ‘That’s guess-work, sir.’

‘It is, which is why we won’t treat it as more than a possibility,’ responded Hemingway, moving over to the door. ‘If I’m right, and Nathaniel locked this door himself, we haven’t got to consider whether the murderer used a pencil and a bit of string to lock the door behind him, because he couldn’t have unlocked it that way. What’s more, they did have the sense to examine the door for signs of rubbing.’

‘Wouldn’t hardly notice on these oak doors, would it?’ suggested the Sergeant. ‘Not like soft paintwork which the string would cut into.’

‘No; but you’d be bound to see some trace under a magnifying-glass. Which would lead one to suppose that the murderer found the door locked, and turned the key from the outside.’