‘It’s just what friends do,’ I say. ‘She’s been there for me plenty of times. She’s always a good listener and judge of character. Her instincts are always right. That’s helped me out a lot over the years. We work well together.’

‘Good,’ Tom says, although I sense from the tone in his voice that his reaction isn’t altogether positive. ‘Just as long as she’s not taking advantage of you.’

I smile. It’s sweet that he’s looking out for me, but he really doesn’t need to. Cath and I are chalk and cheese, but we’ve been close friends for years. She’s always had my back, and it’s encouraging to know that Tom has mine too.

The monarch butterfly is a curious creature. As a caterpillar, it eats only milkweed — a plant that’s poisonous to just about every other animal on the planet, but which forms the sole diet of the monarch caterpillar. They’re completely dependent on this toxic plant.

Once it emerges from its chrysalis as a beautiful monarch butterfly, it no longer needs the poisonous milkweed. Not only that, but it has stored and channeled the poison into its wings — the very things that give it flight.

That’s why the monarch is so successful. It’s learned to not only ignore the poison and be unaffected by it, but to store it up and use it against its own predators.

We can take a lot of lessons from the monarch butterfly. It’s a beautiful, delicate creature. It flutters silently through our gardens, not wanting to harm a soul, yet possessing the power to end lives.

Everyone always thinks they’re good for people, but most don’t realise they’re toxic too. Like you, Catherine Baker.

I know who you are. I’ve done my research. Fortunately for me, you’re one of those people who thrives on gushing their lives onto social media — without even bothering to lock down their privacy settings, of course. #unfortunate.

You’re no good for Grace. You’re toxic. You depend on her to carry out basic functions of your own life. You’re pathetic. You’re a drain on her soul.

Worse than that, I can see you’re going to be a problem. Grace might think you’ve got good instincts, but I can promise you now they aren’t a patch on mine.

If you were so perfect, she’d have been happy long before she met me. But she wasn’t. She was missing something. She was missing me.

6

Friday 6 December

It’s been a while since Cath and I have been out together for a drink. We used to do it regularly when we were younger, and again when Matt left and I needed the friendship — not to mention the alcohol. But things have died down on that front in recent months. I’ve not even seen her in almost two weeks, since the night we tried to fix her seating plan. I get it. I’ve been busy with work, she’s been busy with the wedding preparations.

I’ve been seeing more and more of Tom, too. In fact, we’ve ended up spending most evenings together recently. It’s faster than I’d usually move things, but it just feels right. It seems natural. That’s why I invited her out tonight. Well, one of the reasons, anyway.