Mrs Folliat, he thought, knew all there was to know about Nasse House. Mrs Folliat knew a great deal…Mrs Folliat had known straight away that Hattie Stubbs was dead. Mrs Folliat knew, before Marlene and Hattie Stubbs died, that it was a very wicked world and that there were very wicked people in it. Mrs Folliat, thought Poirot vexedly, was the key to the whole business. But Mrs Folliat, he reflected, was a key that would not easily turn in the lock.

‘I’ve interviewed the lady several times,’ said the inspector. ‘Very nice, very pleasant she’s been about everything, and seems very distressed that she can’t suggest anything helpful.’

Can’t or won’t? thought Poirot. Bland was perhaps thinking the same.

‘There’s a type of lady,’ he said, ‘that you can’t force. You can’t frighten them, or persuade them, or diddle them.’

No, Poirot thought, you couldn’t force or persuade or diddle Mrs Folliat.

The inspector had finished his tea, and sighed and gone, and Poirot had got out his jigsaw puzzle to alleviate his mounting exasperation. For he was exasperated. Both exasperated and humiliated. Mrs Oliver had summoned him, Hercule Poirot, to elucidate a mystery. She had felt that there was something wrong, and there had been something wrong. And she had looked confidently to Hercule Poirot, first to prevent it – and he had not prevented it – and, secondly, to discover the killer, and he had not discovered the killer. He was in a fog, in the type of fog where there are from time to time baffling gleams of light. Every now and then, or so it seemed to him, he had had one of those glimpses. And each time he had failed to penetrate farther. He had failed to assess the value of what he seemed, for one brief moment, to have seen.

Poirot got up, crossed to the other side of the hearth, rearranged the second square chair so that it was at a definite geometric angle, and sat down in it. He had passed from the jigsaw of painted wood and cardboard to the jigsaw of a murder problem. He took a notebook from his pocket and wrote in small neat characters:

‘Etienne de Sousa, Amanda Brewis, Alec Legge, Sally Legge, Michael Weyman.’