‘The valet,’ said the Sergeant.

‘Yes, I’ve thought of him, but I still don’t see it. Even supposing he could have got through, how did he reach the floor?’

‘Supposing he didn’t come in that way, but was there all the time, and escaped through the ventilator?’

‘Worse!’ said Hemingway emphatically. ‘Did he go head first down a ladder?’

‘Not the way I see it,’ said the Sergeant, ignoring this sarcasm. ‘I’ve got an idea he and young Herriard were in this together. It seems to me that if he’d had a chair to stand on he might, if he was clever, have got out through the ventilator. Once his shoulders were through, he could have wormed himself round, and maybe got hold of a drain-pipe, or a bit of that wistaria over the window, to give himself a purchase while he got a leg out. Once he’d got one foot on the ladder he’d be all right.’

‘Seems to me he’d have to be a ruddy contortionist,’ said the Inspector. ‘And what about the chair under the ventilator?’

‘He could have moved that back when the door was forced open. Who’d have noticed? The old fellow would have been taken up with his brother’s body, and if Stephen was in it he doesn’t count.’

‘I can’t see what you want with young Stephen in this Arabian Nights story of yours. Why don’t you let the valet have the whole stage?’ demanded the sceptical Inspector.

‘Because if Stephen wasn’t in it, there wasn’t a motive,’ replied the Sergeant. ‘My idea is that Stephen bribed the valet to help him. I don’t say the valet did the killing: that’s going too far.’

‘Well, I’m glad to know you draw the line somewhere,’ said Hemingway. ‘And don’t you run away with the notion that I’m not pleased with this theory of yours! I’ve always told you that you haven’t got enough imagination, so it’s very gratifying to me to see you taking my words to heart, which is a thing I never thought you did. And if it weren’t for all the circumstances you’ve overlooked, it would be a good theory.’

The Sergeant said in a resigned voice: ‘I know there are some loose ends, but –’

‘Who set the ladder up to be handy?’

‘Either of them.’

‘When?’

‘Any time,’ said the Sergeant, adding after a moment’s reflection: ‘No, perhaps not any time. As soon as it was dark.’

‘Have you ever tried to set a ladder up against a particular window in the dark?’

‘No, sir, I haven’t; but if there was a light in that particular window I’d back myself to do it,’ retorted the Sergeant.

‘You win,’ said Hemingway handsomely. ‘I’ll give you the ladder. And if you can tell me how Ford managed to be in his master’s room and flirting with one of the housemaids at one and the same time, I’ll go straight off and arrest him.’

‘The way I see it, the murder had been committed by the time he came up the backstairs, and went into the sewing-room.’