‘OK,’ said Wexford. ‘Now to return to the curious business of this meal. The idea would presumably be that Kingman intended to kill her that night but that his plan misfired because whatever he gave her wasn’t toxic enough. She was very ill but she didn’t die. He chose those means and that company so that he would have witnesses to his innocence. They all ate the stew out of the same tureen, but only Hannah was affected by it. How then are you suggesting he gave her whatever poison he did give her?’

‘I’m not,’ said Burden frankly, ‘but others are making suggestions. Hood’s a bit of a fool, and first of all he would only keep on about all fungi being dangerous and the whole dish being poisonous. When I pointed out that this was obviously not so, he said Kingman must have slipped something into Hannah’s plate, or else it was the salt.’

‘What salt?’

‘He remembered that no one but Hannah took salt with the stew. But that’s absurd because Kingman couldn’t have known that would happen. And, incidentally, to another point we may as well clear up now – the avocados were quite innocuous. Kingman halved them at the table and the vinaigrette sauce was served in a jug. The bread was not in the form of rolls but a home-made wholemeal loaf. If there was anything there which shouldn’t have been it was in the stew all right.

‘Corinne Last refuses to consider the possibility that Kingman might be guilty. But when I pressed her she said she was not actually sitting at the table while the stew was served. She had got up and gone into the hall to fetch her handbag. So she didn’t see Kingman serve Hannah.’ Burden reached across and picked up the book Wexford had left open at the description and drawing of the shaggy caps. He flicked over to the Poisonous section and pushed the book back to Wexford. ‘Have a look at some of these.’

‘Ah, yes,’ said Wexford. ‘Our old friend, the fly agaric. A nice-looking little red job with white spots, much favoured by illustrators of children’s books. They usually stick a frog on top of it and a gnome underneath. I see that when ingested it causes nausea, vomiting, tetanic convulsions, coma and death. Lots of these agarics, aren’t there? Purple, crested, warty, verdigris – all more or less lethal. Aha! The death cap, amanita phalloides. How very unpleasant. The most dangerous fungus known, it says here. Very small quantities will cause intense suffering and often death. So where does all that get us?’

‘The death cap, according to Corinne Last, is quite common round here. What she doesn’t say, but what I infer, is that Kingman could have got hold of it easily. Now suppose he cooked just one specimen separately and dropped it into the stew just before he brought it in from the kitchen? When he comes to serve Hannah he spoons up for her this specimen, or the pieces of it, in the same way as someone might select a special piece of chicken for someone out of a casserole. The gravy was thick, it wasn’t like thin soup.’