After they had lunched Alleyn brought his report up to date and Fox, sitting solemnly at the parlour table, typed it in duplicate. Alleyn had a brief interview with Abel Pomeroy and returned with three tumblers. One of these he smashed to splinters with the poker, keeping the pieces together, and emptying them into a tin. The other two he wrapped up and placed, with a copy of his report, in his case. He also spent some time throwing down darts and finding that they stuck in the floor. These employments at an end, they drove to Illington. The day had turned gloomy, heavy rain was falling, and the road was slimy.

Alleyn dropped Fox at Woolworth’s and went on to Dr Shaw’s house at the end of the principal street. He was shown into a surgery that smelt of leather, iodine, and ether. Here he found Dr Shaw. He had an air of authority and a pleasing directness of manner.

‘I hope I’m not an infernal nuisance, coming at this hour,’ said Alleyn. ‘Your patients—’

‘That’s all right. Surgery doesn’t start till two. Old trot sitting out there in the waiting-room. Malade imaginaire. Do her good to wait a bit, she plagues my life out. Sit down. What do you want to talk about?’

‘Principally about the wound and the dart. I’ve read the police report of the inquest.’

‘Thought it rather full of gaps? So it is. Mordant, the coroner, you know, is a dry old stick, but he’s got his wits about him. Respectable bacteriologist in his day. He and Harper got their heads together, I imagine, and decided just how much would be good for the jury. What about the wound?’

‘Were there any traces of cyanide, prussic acid, or whatever the blasted stuff is?’

‘No. We got a man from London, you know. One of your tame experts. Good man. Mordant and I were both there when he made his tests. We didn’t expect a positive result from the wound.’

‘Why not?’

‘Two reasons. He’d bled pretty freely and, if the stuff was introduced on the dart, what wasn’t absorbed would be washed away by blood. Also, the stuff’s very volatile.’

‘They found the trace on the dart.’

‘Yes. Oates kept his head and put the dart into a clean soda-water bottle and corked it up. Couldn’t do that with the finger.’

‘Even so, wouldn’t you expect the stuff to evaporate on the dart.’

Dr Shaw uttered a deep growl and scratched his cheek.

‘Perfectly correct,’ he said, ‘you would. Puzzling.’

‘Doesn’t it look as if the Scheele’s acid, or rather the fifty per cent prussic acid solution, must have been put on the dart a very short time before Oates bottled it up?’

‘It does. Thought so all along.’

‘How long was it, after the event, that you got there?’

‘Within half an hour after his death.’