thought it was still legal to experiment on animals.’

‘It is still legal,’ Kurt says.

‘Not in schools. The Head says that rat was Mr Critchley’s pet,’ Frankie points out.

‘Maybe,’ Kurt shrugs. ‘Maybe not. I don’t trust him. He used to keep rats in the lab and kill them so the kids could dissect them, just to show stupid, random stuff, like how long a rat’s intestine is.’

‘Yuck,’ Frankie says. ‘That’s like something from the dark ages!’

‘It wasn’t so long ago,’ Kurt says. ‘My dad went to St Peter and Paul’s, back in the nineties, and Mr Critchley taught him. Dad got excluded for three days, once, for refusing to cut up a rat.’

Lily pulls a face. ‘Don’t tell me,’ she says. ‘I bet your dad’s some saddo hippy loser, just like you.’

Kurt blinks. ‘My dad’s dead,’ he says quietly. ‘He and my mum were killed in a car crash when I was three.’

A shiver runs down my spine, and my cake fork drops on to the tabletop with a clatter.

Lily is mortified. ‘I’m sorry!’ she whispers, her face pale. ‘I didn’t know, Kurt, honest…’

‘Oh, Kurt,’ Frankie echoes. ‘That’s just so sad!’

He shrugs. ‘I was only a toddler,’ he explains. ‘I don’t remember much about them, but I live with my gran, and she tells me stories of the things Dad used to do. I couldn’t believe it when I heard the rat story. I never did like Mr Critchley, but knowing that he got my dad excluded like that –’

‘The loser!’ Lily says angrily. She has changed sides instantly. ‘I’ve always said Critchley is a creep…’

‘And he still keeps a rat in his classroom,’ Frankie breathes. ‘What a sicko!’

‘I guess my dad might have been a bit like me,’ Kurt is saying. ‘He was the sort of person who stood up for what he believed in, and… well…’

Lily’s mouth drops open. ‘It was you!’ she gasps. ‘You stole Mr Critchley’s rat!’

Kurt smiles. ‘I prefer to think of it as a rescue,’ he says.

‘But what… where…’

‘Don’t worry, Lily,’ Kurt assures her. ‘The rat is in a safe place.’

I am glad Lily is sitting on the other side of the table, because that means she can’t see the twitching pink nose that pokes out briefly from Kurt’s rucksack, then disappears again.

‘Hang on,’ Lily argues. ‘Where exactly…’

I chew my lip. If Lily spots the rat, things could get very nasty. A repeat performance of the canteen rat-riots is not what Heaven needs at all.

Luckily, at that moment the steamed-up cafe door swings open and Dan Carney comes in, his black hair plastered to his head, wings dripping.

‘Dan!’ Lily yells. ‘Over here! I’ve been saving you a seat!’

Dan picks his way through the crowded cafe ‘Hey!’ he says. ‘You wouldn’t think it could be so hard to give away free cake!’

‘You should have ditched them into the nearest bin,’ Lily says.

Dan frowns. ‘No, I wanted to do it properly,’ he says. ‘Move up, Frankie, huh?’ Frankie shuffles along into the seat beside Lily, and Dan flops down next to me with a wink. Lily’s smile has turned upside down, but my heart just about flips over.

‘I handed one to a woman whose umbrella had blown inside out,’ Dan is saying. ‘Then there were two little kids in wellies and a guy selling The Big Issue on the corner. I gave him three.’

Dan hangs the dripping angel wings on the back of his chair, grinning, and I find myself grinning right back. He shrugs off his wet jacket to reveal a tight black T-shirt with Heaven printed across the chest, and that’s kind of appropriate as right now I think maybe I’ve died and gone there.

Being invisible is dangerous, obviously, because once you start to materialize again you feel pretty grateful to anyone who happens to notice you’re alive. That’s all it is, I tell myself. It’s not like I am falling for a boy who tears up exercise books and sets fire to his desk.

Even I can see that would be a very bad idea…

I finish my last mouthful of strawberry cream sponge with a sigh.

‘Oi,’ Lily says, jabbing Frankie in the ribs. ‘Didn’t you lot say you had to be going?’

‘Did we?’ Frankie echoes.

‘Yes, you did,’ she insists. ‘Places to go, things to do, that’s what you said.’

‘I’d better head off, anyway,’ Kurt admits. ‘My gran will be wondering where I am.’

‘I, also,’ I say. The three of us get to our feet and Lily grins and shifts along a little to sit closer