‘I shall be all right if I lie down,’ Mathilda replied. ‘It’s nothing much: I often get these heads.’

‘Come on, Joe, leave her alone!’ said Stephen, opening the door into the drawing-room. ‘Tea!’

‘With you in one moment, old man!’ Joseph said. ‘I’m just going to wash my hands.’

Mathilda had gone upstairs. Stephen heard her cross the hall above, and go into her room. He watched Joseph follow trippingly in her wake, smiled grimly, and went into the drawing-room.

The Inspector, emerging from the library, found the coast clear, and went at once to the first half-landing. Dropping on his knees there, he closely scrutinised the stair-carpet. It was a thick, grey pile, and here and there a few small stains were visible on it. The Inspector discovered two brown spots on the half-landing, and, having looked at them through his magnifying-glass, produced a safety-razor blade from a small case in his pocket, and carefully cut these away from the carpet. He placed the severed tufts of pile in a container, and rose from his knees. ‘I’m going back to the station,’ he said briefly. ‘You stay here and keep your eye on our clever customer. It’s just on the cards he may have been listening outside the library door. Tail him!’

The Sergeant, who had been thinking deeply, said: ‘Chief, if it’s true – why did he stab him in the back? That wasn’t how that chap killed the Empress, according to what you read out!’

‘Because, for one thing, any sharp pain in the back Nathaniel would think was his lumbago. For another, I’d say kind Uncle Joseph put in a bit of anatomical research, and chose the best place for his purpose.’

‘But what a risk!’ said the Sergeant. ‘Suppose it hadn’t come off? Suppose the old man had dropped down there?’

‘He wasn’t likely to do that. If he’d turned faint at once, no doubt Joseph would have helped him up to his room, and left him there. Don’t forget he thought he’d got rid of the rest of the house-party! He had to take a risk. Keep your eye on him!’

He left the house, and a minute later the Sergeant heard the police-car outside start up and drive away.

It was nearly three hours later when Inspector Hemingway again entered Lexham Manor. He was admitted by Sturry, who said, in a portentous voice, that he was glad to see him.

‘Well, that’s something new,’ said Hemingway. ‘Quite brightens up my day. Ask Mr Stephen if he can spare me a moment, will you?’

‘I will inform Mr Stephen that you are here, Inspector,’ said Sturry. ‘In the meantime, a very Peculiar Thing has occurred, of which I feel you should be instantly apprised.’

‘You can’t apprise me of anything I don’t already know, so don’t try!’ said Hemingway briskly. ‘Get hold of Mr Stephen for me!’

Swelling with affronted majesty, Sturry walked away.

In a very few minutes Stephen came into the hall. ‘Thank the lord you’re back!’ he said. ‘Joseph’s disappeared. We’ve no idea where he is. Hasn’t been seen since he went up to wash his hands before tea.’