Alleyn elaborated his theory of the trout, the punt and the daisies, building up a complete and detailed picture of one way in which Colonel Cartarette might have been murdered. ‘I realize,’ he said, ‘that it’s all as full of “ifs” as a passport to paradise. Produce any other theory that fits the facts and I’ll embrace it with fervour.’

Fox said dubiously: ‘Funny business if it works out that way. About the punt, now …’

‘About the punt, yes. There are several pieces of cut grass in the bottom of the punt and they smell of fish.’

‘Do they, now?’ said Fox appreciatively, and added: ‘So what we’re meant to believe in is a murderer who sails up to his victim in a punt and lays him out. Not satisfied in his own mind that the man’s dead, he steps ashore and has another go with another instrument. Then for reasons you’ve made out to sound OK, Mr Alleyn, though there’s not much solid evidence, he swaps the Colonel’s fish for the Old ’Un. To do this he has to tootle back in the punt and fetch it. And by way of a change at some time or another he swipes the heads off daisies. Where he gets his weapons and what he does with the first fish is a great big secret. Is that the story, Mr Alleyn?’

‘It is and I’m sticking to it. Moreover, I’m leaving orders, Oliphant, for a number one search for the missing fish. And meet me,’ Alleyn said to Fox, ‘on the other bank. I’ve something to show you.’

He gathered up the long tow rope, pulled himself easily into the contra-current and so back across the stretch of water to the boat shed. When Fox, having come round by the bridge, joined him there, he was shaking his head.

‘Oliphant and his boys have been over the ground like a herd of rhinos,’ he said. ‘Getting their planks last night. Pity. Still … have a look here, Fox.’

He led the way into a deep hollow on the left bank. Here the rain had not obliterated the characteristic scars left by Lady Lacklander’s sketching stool and easel. Alleyn pointed to them. ‘But the really interesting exhibit is up here on the hillock. Come and see.’

Fox followed him over grass that carried faint signs of having been trampled. In a moment they stood looking down at a scarcely perceptible hole in the turf. It still held water. The grass nearby showed traces of pressure.

‘If you examine that hole closely,’ Alleyn said, ‘you’ll see it’s surrounded by a circular indentation.’

‘Yes,’ Fox said after a long pause, ‘yes, by God, so it is. Same as the injury, by God.’

‘It’s the mark of the second weapon,’ Alleyn said. ‘It’s the mark of a shooting-stick, Brer Fox.’

II