‘Read them. See if you can spot the odd one out. That’s the last piece of the puzzle – it was for me and it will be for you. No, on second thoughts, this isn’t charades at Christmas.’ Simon put his pasta bowl down on the floor and stood up. ‘Where are they? Still on the kitchen table?’

He returned with a handful of papers a few minutes later. ‘Here. This is the one you need to read.’

‘You’re telling me which is the odd one out?’ Charlie squinted up at him suspiciously. ‘You’re helping me to get the answer?’ There was no precedent for this.

‘The other two stories are Lane Baillie standard issue – naïve moral message, be kind, give off positive energy, think the best of everyone. Lane Baillie knows the other two stories. She gives them out to her clients. This one, the odd one out – she’s never heard of it. Billy sent it to Sondra Halliday, but Lane had never laid eyes on it till I put it in front of her. I don’t think she was impressed by the general principles it promotes. She described it as “concerning”.’

‘Can we stop saying “Billy”?’ Charlie asked. ‘Isn’t it Faith Kendell AKA Isobel Sturridge we’re talking about here?’

Simon’s face froze – as if he were trying to imitate a wax model of himself. ‘Is it?’ he said. ‘Why do you say that?’

‘Because the evidence suggests that Billy Dead Mates is Isobel Sturridge – doesn’t it?’

‘A lot of it does, yes.’

‘But not all of it?’

‘Why would Isobel Sturridge want to kill Linzi Birrell? Why would she want to kill Josh Norbury?’

‘All right, fine,’ Charlie snapped. ‘Billy it is.’ She tried to expel all the air from her lungs, hoping to breathe out her frustration along with it. After inhaling new supplies to see her through the next stage of the conversational ordeal, she said, ‘So if one of the stories Billy sent Sondra Halliday didn’t come from Lane, maybe he wrote it himself.’

‘Correct,’ said Simon.

‘Twice in one day! I intend to let this go to my head.’

‘Not only is the moral of the story very different from the others, it also sticks out like a sore thumb linguistically. Billy’s a Brit, so “favourite”, “neighbour” – those words contain a “u” when Billy writes them. And words like “realise” are spelled “i-s-e” not “i-z-e”. The stories on Lane’s website were written by an American – hardly surprising – so we have “neighbor”, “favorite”, “realize” with a zed. Or a zee, as a Yank would say.’

‘Billy snuck in a story of his own, camouflaged within Lane’s collection,’ said Charlie.