It’s my birthday tomorrow, my thirteenth.

It hasn’t rained for weeks now. The Links is getting yellow and dry, and the cloudless evening sky is a flat, endless, deep violet.

We would do this tomorrow evening on my actual birthday, but Dad has to fly back to New Zealand to sort out some stuff, so we’ve brought it forward a day.

Is it a birthday party? Not really. I didn’t want it to be – it’s more important than that.

Besides, it would be the strangest thirteenth birthday party guest list, all of us gathered on the big flat rock underneath the lighthouse.

There’s:

• Me, obviously.
• Gram.
• Lady.
• Boydy and his mum AND his dad, who is out of jail on a day licence, which is when you’re allowed out to see your family. (He’s nice. Basically, an older, fatter version of Boydy, and not at all criminal-looking. Boydy’s mum is smiley and shy.)
• Mrs Abercrombie and Geoffrey. (I know, but I kind of had to invite her because I wanted Gram to have a friend there – and anyway, she’s much nicer to me now that Geoffrey has stopped growling at me. She’d be even nicer if she knew it was down to me that she got her reward money back.)
• Revd Henry Robinson.
• Kirsten Olen (who I have now told about mum/Felina, but not about the invisible stuff. Not yet).
• The same guy from the Whitley News Guardian who was at Great-gran’s hundredth. (Boydy’s local hero status is about to be further enhanced and he’s going to become even more bumptious, but I don’t mind so much now.)
• And – of all people – Mr Parker, and a jolly lady called Nicky who he introduced as his partner. (I had not had Mr Parker down as the sort to have a girlfriend. Mr Parker, it turns out, is a secret lighthouse enthusiast. He told Boydy that he could borrow the music department’s mixing desk and amplifiers, and even went into school in the holidays to collect them. I thought that was quite a big deal, but Mr Parker called it ‘a mere trifle for a fellow pharophile’.)

Nothing, and no one, it is turning out, is what they first appear.

Boydy is pacing up and down, looking all nervous. He had a haircut last week, and shaved off the fluff that was on his chin, which looks much better, and in fact there’s not much of a double chin under the fluff after all. He’s also got himself some new clothes. It’s nice: it’s like he’s dressed up for the occasion. Not sure about the patterned shirt, to be honest, but at least his new stuff fits him. I found him a lighthouse keeper’s cap on eBay (who knew there were such things? Not me), which he loves.

There is another guest yet to arrive. Dad has gone to get Great-gran from Priory View. Normally all the residents are in bed by nine, and they were very reluctant to let her go.

‘Let her go?’ I heard Dad say on the phone to them. ‘Are you keeping her prisoner or something, or is she a paying guest?’

That did it.

Only, they’re late. Which wouldn’t normally be much of a problem, but the causeway will be beneath water in about twenty minutes and we’ll be stuck on St Mary’s Island overnight.

We’re all anxiously peering along the causeway and up to the car park, hoping to see headlights coming towards us in the twilight.

Dad wouldn’t miss this, would he?

I’m wearing Mum’s T-shirt, the one that still smells of her a bit. I know it might change the smell, but somehow I don’t mind. Not tonight.

‘There they are!’ calls Boydy, pointing to a pair of headlights coming towards us, and I breathe a small sigh of relief.

Next to Dad is Great-gran, a tiny figure in the passenger seat. When the car pulls to a halt at the bottom of the steps, near to the flat rock, I can see someone else as well, a man, sitting in the back seat.

‘Who’s that?’ I ask Gram, but she has no idea.

We already have a wheelchair waiting, and I push it to the car to help Great-gran out.

‘Stanley?’ I say when I get nearer and see who the old man in the back is.

‘Yeah,’ chuckles Dad. ‘Your great-gran didn’t want to come without her boyfriend, did you, Mrs Freeman?’

Great-gran smiles broadly and nods as she eases herself into the wheelchair, then she smiles her watery smile at me and says, ‘Hello, hinny.’

Dad takes over the wheelchair while I go round and help Stanley out. He’s frail, but steady on his feet.

‘Hello, Boo,’ he says in a reedy old-man voice. ‘I’ve heard all about you. It’s very nice to see you.’

(It’s only afterwards that I wonder what he meant by that. Was it a reference to my invisibility? Has Great-gran told him? I’m surprised to discover that I don’t really mind either way.)

‘Let us pray,’ says Revd Robinson.

And as we all clasp our hands and start to mumble the Lord’s Prayer, I keep my eyes open and look around at the gathering.

“Our father, which art in heaven …”

Old Stanley stands behind Great-gran’s wheelchair and adjusts her woollen shawl for her. Great-gran hasn’t closed her eyes, but instead is focusing on a point far out to sea. Her lips move as she mouths the familiar words.

Mrs Abercrombie has put Geoffrey down on the ground and he’s much happier, sniffing around a rock pool with Lady.

Kirsten is in charge of the music, and stands behind the school’s mixing desk.

Everyone says, ‘Amen’, and there’s a pause while a pair of seagulls answer loudly overhead.

‘Are we ready?’ asks Boydy.

‘Hang on, hang on!’ I say.

From my pocket I bring out a packet of Haribos, and open it, tipping them onto my hand. I give them out, one for each person.

‘Some of you will remember that these were my mum’s favourite,’ I say, and everyone has a sad smile as they start chewing.

Dad has to take his nicotine gum out first.

I nod over at Kirsten, who slides up a fader. Mum’s song blasts out, rich and loud:

‘You light up my life when I see you

And all I want is to be with you …

You light the light in me –

Come on, baby, light the light!’

When Mum sings ‘light the light’, Boydy flicks the switch on the extension cord snaking up the lighthouse, and the light of a million candles drenches the flat rock, beaming down from the glass-encircled top thirty-eight metres above us.

It lights up the whole beach.

It lights up the sea.

It lights up the whole world, it feels like.

Stanley cheers, and claps and shouts, ‘Bravo!’

And everyone else follows his lead.

Gram reaches down into her canvas bag and hands me the carved brass vase with the lid that I saw in her cupboard the day I went rummaging. It feels like a lifetime ago, and – in a way – it was.

I take a sniff of the T-shirt I’m wearing, then prise off the lid.

As Mum’s song continues to play, and people suck their sweets, I hold up the urn to let the dusty contents spill out, and they are immediately carried away on the wind out to sea. One or two ashes have fallen by the rocks, and a wave soon swishes over them. In a few seconds not a single bit remains in the air or on the ground.

I look around. Everyone is crying. Not loud, not sobbing, but Gram is wiping her eyes, and even Dad has this funny expression like he’s struggling not to cry. Boydy’s mouth has that upside-down smile that I have seen before.

Lady has lain down on the rock and is looking out to sea.

I say, ‘everyone is crying’ – well, everyone but me.

Me? I’m grinning!

Everything is right; everything is perfect.

Dad has come up behind me and squeezes my shoulders, and Gram’s holding my hand.

‘Bye, Mum!’ I say, and I wave out to sea with my other hand.

That’s when I decide that I’m going to be Ethel. Ethel Leatherhead. Family nickname: Boo.

That’s who I am.

No one has noticed that the causeway is now completely underwater. It’s going to be an interesting night.