Rosemary frowned.

‘I hadn’t thought of that.’

Dorothy sipped her tea.

‘Cocoa would be better,’ she said.

‘But that’s already sugared,’ objected Rosemary.

Dorothy’s needles clacked assiduously.

‘Yes, but it tastes so strong that you could add poison without the victim noticing.’

Rosemary shook her head.

‘You’ve still got the same problem, Dot. The mugs of cocoa are just left out on a tray in the hall. There’s no way of making sure that the poison reaches the right person.’

Dorothy set down her knitting. She cradled the tea cup in her hands, as though to warm them.

‘I always take the blue one. Most people use the same mug every night. Yours is the brown one with the broken handle glued back on. Charles likes the dark green one, while Grace prefers the pale pink. Weatherby always uses that hideous coronation mug, and Mrs Hargreaves…’

‘You haven’t really changed your will, have you Dot?’ Rosemary interrupted.

Dorothy picked up her knitting without answering. Rosemary looked at her friend with a preoccupied expression.

‘It’s none of my business, of course,’ she went on, ‘but I must say that I would personally consider it most unwise to put any faith in promises which may have been made in a certain quarter. I shouldn’t think there’s the slightest chance of their being honoured.’

Dorothy clutched her chest and moaned.

‘What is it?’ cried Rosemary in alarm.

‘I’m all right. Only would you be an angel and fetch my medicine? What with one thing and another I never did manage to get upstairs, and now it’s started to hurt quite badly.’

‘Is there anything else?’ asked Rosemary, springing to her feet.

Dorothy tried a smile which did not quite come off.