‘Mr Juniper got in a great way when I started asking questions. I went very easy with him, but he made me a regular speech about how careful he is and showed me his books. He reckons he always double-checks everything he makes up. He’s particularly careful, he says, because of Dr Withers being uncommonly fussy. It seems they had a bit of a row. The doctor reckoned the kids’ medicine wasn’t right, and Juniper took it for an insult. He says the doctor must have made the mistake himself and tried to save his face by turning round on him. He let on the doctor’s a bit of a lad and a great betting man, and he thinks he’d been losing pretty solidly and was worried, and made a mistake weighing the kids or something. But that wouldn’t apply to Sir Henry’s medicine, because it was the mixture as before. And I found out that at the time he made it up he was out of arsenic and hasn’t got any yet.’

‘Good for Mr Juniper,’ said Alleyn dryly.

‘Which brings us,’ Fox continued, ‘to this tin.’ He laid his great hand beside it on the desk. ‘Bailey’s gone over it for dabs. And here we have got something, Mr Alleyn, and about time too, you’ll be thinking. Now this tin has got the usual set of prints. Some of the search party’s, in fact. Latent, but Bailey brought them up and got some good photographs. There’s Mrs Kentish’s. She must have just touched it. Miss Desdemona Ancred seems to have picked it up by the edge. Mr Thomas Ancred grasped it more solidly round the sides and handled it again when he took it out of his bag. Mrs Henry Ancred held it firmly towards the bottom. Sir Cedric’s prints are all over it, and there, you’ll notice, are the marks round the lid where he had a shot at opening it.’

‘Not a very determined shot.’

‘No. Probably scared of getting rat-bane on his manicure,’ said Fox. ‘But the point is, you see—’

‘No Orrincourt?’

‘Not a sign of her. Not a sign of glove-marks either. It was a dusty affair, and the dust, except for the prints we got, wasn’t disturbed.’

‘It’s a point. Well, Fox, now Bailey’s finished with it we can open it.’

The lid was firm and it took a penny and considerable force to prise it up. An accretion of the contents had sealed it. The tin was three-parts full, and the greyish paste bore traces of the implement that had been used to scoop it out.

‘We’ll have a photo-micrograph of this,’ Alleyn said.

‘If Orrincourt’s our bird, sir, it looks as if we’ll have to hand the tin over to the defence, doesn’t it?’