‘I remember what happened next as clearly as if it were yesterday,’ Evelyn said. ‘It was like something out of a film. I was shouting at Joan that I didn’t believe her, and Joan was shouting at me that I hadn’t had to put up with Scarlet’s whingeing and snivelling. I told her she was being ridiculous, that Scarlet was only three, and Joan said that was old enough to know how to behave.’

Evelyn was describing the row so clearly that Pip could imagine the scene. She pictured the two women on the landing outside Scarlet’s bedroom, nose to nose as they screamed at one another.

‘I could see I was getting nowhere,’ continued Evelyn, ‘so I made a huge effort to bring the temperature back down. I asked Joan, as calmly as I could, to just tell me the truth. She didn’t have the stomach for the fight any more than I did. She said Scarlet had been moaning, that she wanted a drink, or something to eat, or was too hot or too cold, and so she had put her outside to play so she could get on with the housework without the constant interruptions, and that was when she had just wandered off into next door’s garden. But, you see, that didn’t make any sense to me. I knew that all Scarlet wanted was to sit quietly with a book because her head cold was making her feel so rotten.’

Pip’s heart was in her throat. She was desperate for Evelyn to reach the story’s resolution, but didn’t dare interrupt. Instead she refilled their cups, even though Evelyn had barely touched her first one.

‘And that’s when it finally dawned on me what had happened,’ Evelyn said, her expression suddenly steely. ‘Joan must have locked her out of the house. The reason why Scarlet didn’t come back inside when she’d had enough, and wandered away into next door’s garden to drown in their pond, was because the door was locked and she couldn’t get in.’

Pip’s mouth fell open. ‘Oh, my God,’ she said, horrified.

If that was what had happened, if Joan really had barred the door against three-year-old Scarlet, then that was unforgivable. And if Evelyn really had killed her sister, surely that would be justification enough. Pip tried to imagine how it would feel to be Joan, knowing you had something like that on your conscience, but she drew a blank. It was, arguably, even worse than the dark shadow on her own conscience.