‘Whoops!’ I say.

Elsa’s head falls back and she laughs so hard that it’s impossible not to join in. Then I realise that the prickle has faded away to nothing.

It’s amazing what a positive effect a hairy bum can have on your mood.

THIRTY

Back at school, Ed and I don’t talk about Saturday, and we certainly don’t share any lightning-quick waves. The first time I see him is in maths and he arrives after the lesson has started. A paranoid part of me wonders if he’s done this on purpose, but he doesn’t do anything else to suggest he’s avoiding me. In fact, it’s like the hair rubbing and electric shock never happened. Two minutes into the lesson, he leans towards me and whispers, ‘Got a pen?’ and that’s it. Everything’s back to normal, with Ed checking his score against mine in an equations test and casually asking if I’m ready to be ‘totally destroyed’ in the NASA competition as we leave the room.

I’m actually more nervous about going to science and seeing Bella, and discovering if Ed’s told her about the Cool Cosmos show. But it’s business as usual and as the lesson goes on, and Bella squabbles with Raj about a calculator and calls me a ‘nerdasaurus’ for owning a pen with a spirit level, I realise Ed can’t have told her about Saturday.

And I’m relieved, of course I am – if Ed had told her everything I’d done, Bella would have destroyed me – but I’m also left feeling a bit flat. I thought that something changed on Saturday, and that the way Ed and I had laughed and talked as we went round the science centre would transfer to school in some way. But it looks like I got that wrong: Bella and Raj are arguing, Ed’s rolling his eyes and joining in occasionally, and I’m just sitting here in silence, like I’m invisible.

Nothing’s changed at all.

THIRTY-ONE

‘Don’t talk to me, Meg,’ says Ms Edgecombe. ‘I need to concentrate on not killing anyone.’

It’s the next day and I’m sitting at the front of the minibus beside Ms Edgecombe as she drives us to Sussex University. Not talking suits me as it gives me time to text Grandad to remind him to pick up Elsa. It also means I get to stare out of the window, watch the countryside fly past, and think about Little Acorns, or, more precisely, Dawn.

I’m not sure if I’m being paranoid, but this morning Dawn started asking me questions about Mum. It felt like she was trying to catch me out. ‘Did you get Elsa’s bag ready today?’ she asked. When I told her that I put everything in and then Mum checked it, she narrowed her eyes and said, ‘Riiight,’ really slowly. Then she asked why Mum had stopped putting in organic baby wipes. ‘Too expensive,’ I said, deciding to stick to the truth.

I’m glad Grandad’s picking Elsa up this afternoon. He’s a much better liar than me.