Sergeant Oliphant and PC Gripper came forward with a stretcher. They put it down some distance from the body which they now raised. As they did so a daisy-head, crumpled and sodden, dropped from the coat.

‘Pick it up, tenderly,’ Alleyn said as he did so, ‘and treat it with care. We must find the other two if we can. This murderer said it with flowers.’ He put it away in his case. Oliphant and Gripper laid the body on the stretcher and waited.

Alleyn found a second daisy on the bank below the point where Colonel Cartarette’s head had lain. ‘The third,’ he said, ‘may have gone downstream, but we’ll see.’

He now looked at Colonel Cartarette’s rod, squatting beside it where it rested on the bank, its point overhanging the stream. Alleyn lifted the cast, letting it dangle from his long fingers. ‘The fellow of the one that the Old ’Un broke for him,’ he said.

He looked more closely at the cast and sniffed at it.

‘He hooked a fish yesterday,’ he said, ‘there’s a flake of flesh on the barb. Where, then, is this trout he caught? Too small? Did he chuck it back? Or what? Damn this ruined ground.’ He separated the cast from the line and put it away in his case. He sniffed into the dead curved hands. ‘Yes,’ he said, ‘he’s handled a fish. We’ll go over the hands, fingernails, and clothes for any more traces. Keep that tuft of grass that’s in his hand. Where’s the rest of it?’

He turned back to the riverbank and gathered up every blade of grass that was scattered where the Colonel had cut it. He examined the Colonel’s pocket-knife and found that, in addition to having traces of grass, it smelt of fish. Then he very cautiously lifted the Old ’Un and examined the patch of stones where the great fish had lain all night.

‘Traces there, all right,’ he said. ‘Are they all off this one fish, however? Look, there’s a sharp flinty bit of stone with a flap of fish skin on it. Now let’s see.’

He turned the great trout over and searched its clamminess for a sign of a missing piece of skin and could find none. ‘This looks more like business,’ he muttered, and took out his pocket lens. His subordinates coughed and shifted their feet. Fox watched him with calm approval.

‘Well,’ Alleyn said at last, ‘we’ll have to get an expert’s opinion and it may be crucial. But it’s pretty clear that he made a catch of his own, that it lay on this patch, that a bit of its skin was torn off on this stone, that the fish itself was subsequently removed and the Old ’Un put in its place. It doesn’t look as if it was chucked back in the stream, does it? In that case, he would have taken it off his hook and thrown it back at once. He wouldn’t have laid it down on the bank. And why was a flap of its skin scraped off on the stone? And why was the Old ’Un laid over the trace of the other fish? And by whom? And when?’