Gibbs agreed it was ludicrous to imagine what I was imagining. The best way to prove how unlikely it was, I suggested, was to check Faith was all right, maybe offer her some protection. What harm would that do? Because, let’s face it, if that white book wasn’t intended for her, who was it meant for? There were no other candidates for the role of best friend to me on Ward 10 of the RGI that day. It had to have been meant for Faith – who, by the way, I’m sure would start to irritate the hell out of me if I ever got to know her better. I was already getting a bit sick of her by the time I’d finished giving DC Gibbs as complete a description of her as I could remember – small frame, black hoody, baggy jeans, very short brown hair, brown eyes.

Could Billy have pinned up that little white book on the board and then sent someone in that he’d lined up to befriend me artificially? This, I decided, was the single most ludicrous suspicion I’d ever had.

Still, I tried as hard as I could to persuade Gibbs that Faith Kendell might be in danger, not because I thought it was likely but because I believed there were no other possibilities.

Don’t ever think that, boys and girls. Don’t be as naïve as I was. There are always other possibilities and plenty of them – ones you couldn’t come up with in your most demented dreams. Or at least I couldn’t, and neither could Chris Gibbs.

Detective Constable Simon Waterhouse on the other hand – he was a different story.

Typed copy of handwritten letter received by Sondra Halliday on 4 January 2015

2 January 2015

Dear Mrs Halliday

I hope you don’t mind me addressing you as such. Your Wikipedia entry tells me you’re married to the chef Oliver Halliday, so it seems the obvious thing to call you.

I hope you enjoy the enclosed novel, Beloved by Toni Morrison. It is a work of genius in my opinion. You might wonder why I, a complete stranger, am sending you a book. It’s because I want to teach you. I don’t know if you’re capable of learning, but I have to try.

(“Why?” I imagine you asking.)

I have to teach you because the only other thing I want to do to you is kill you. Nearly every day, you are doing severe harm to the thing that matters to me most in the world. You have your cause and I have mine; they are not the same thing. They are, rather, stratospheres apart – and you’ve been lying about my agenda in order to further your own. I have an itch inside me, telling me that the only thing I can do to stop this is put an end to you. Then this thing I care about won’t be ruined.