The good news: I’m on a spy-training mission and I have a bag full of uber-cool gadgets.

The bad news: I am in the women’s underwear section of a department store and surrounded by BRAS.

I used to be Joe – until one day Mum and Dad told me they were spies who had to go on the run because their cover was blown. It meant a whole new life – new house, new school, new name. So far, so great – who wouldn’t want parents with the excuse to drive too fast and use spy gear? But then they told me that to keep us from discovery, I had to go undercover – as a girl.

Yeah, exactly.

Not only do I have to dress as a girl, I have to dress as Dad’s idea of a girly girl. He thinks it’s only by having a completely over-the-top girl disguise that my real identity will stay a secret. Which is why I’ve been forced to wear ruffles, bows, sparkly hair clips in an assortment of animal shapes and way, way, WAY too much pink.

There are only two things that make me feel better about all this:

1. Sam – my one good friend since all this began. She lives a few doors away and goes to the same school as me. She loves football as much as I do and would never wear pink. She even likes my favourite fictional hero, Dan McGuire, who’s a spy like us, except just in books.

2. Sam and I are being trained as professional spies. We’ve already completed two spy missions – our first unofficial one, when we caught a teacher stealing school funds, and then an official operation when we stopped a dance teacher from pinching the contents of a football memorabilia exhibition. (That mission meant we had to take ballet lessons and put on tutus … I don’t want to talk about it any more.)

Now we’re on a training mission set up by my dad (which is probably how I’ve ended up surrounded by the bras). We’ve got to pick up a secret message and avoid being caught by an ‘enemy spy’ (Dad). Okay, it’s not the best setting for an exciting spy mission but ever since my undercover life began, I’ve realised you have to work with what you’ve got.

I move away from a display of giant granny knickers and reach up to press the Ring-a-Ring spy phone clipped to my ear. It’s one of our most useful bits of spy kit – a walkie-talkie disguised as an earring. ‘Have you found it?’

‘Yes, got it,’ Sam’s voice says. She’s across the way in Textiles – we were assigned different departments to search and of course I was given the embarrassing one. Sometimes I wonder if my parents are out to get me.

‘I’ll meet you in Lighting,’ I tell her.

‘See you in five.’

I cut the connection off and turn to go – and find myself facing a smiling sales assistant. ‘Do you need some help, dear?’

‘Uh, no thanks,’ I say.

The woman reaches out and pats me on the arm. ‘I know it can be embarrassing when you’re buying your very first bra. Why don’t I select a few for you to try on? You could wait in the changing rooms and I could hand them in to you.’ She gestures at the rack I’m standing next to. I flinch as I realise I’m right by the training bras. There’s a sign next to them that says ‘For the developing young lady’. For a second it feels like my feet are encased in cement, rooting me to the floor, even though my brain is screaming one word, over and over and over: RUN! RUN! RUN!

‘How about this one with the little pink flowers – it’s ever such a pretty design.’ The woman plucks a hanger with a pink strappy thing hanging from it and dangles it in front of me.

My face feels like it’s been shoved in the oven – I must look like a red pepper. ‘No, really, I’d better go – I’m meeting my mum,’ I stutter, backing away.

‘All right, dear, but if you change your mind about me helping, I’ll be right here.’ The woman smiles at me kindly. You can tell she’s thinking that I’m too shy to let her help me and that I really do want a bra.

What I really want is to take off this dress that’s covered with small yellow bananas and PUT MY TROUSERS BACK ON.

I’m just about breathing normally when I get to the safety of the second floor. To be extra careful, I slip into the stairwell near the lifts, pull out a raincoat from my rucksack and shrug it on over my dress. Mum and Dad have trained us to change our appearance as often as possible to lose anyone who might be tailing us. I step out into the nice, normal lamps and lampshades of the lighting department and breathe in the un-bra-tainted air. Sam walks up holding a four-pack of 50-watt light bulbs.

‘What are those for?’

‘I needed to look like I was shopping for something – that assistant over there was looking at me like I was planning a robbery. He must have seen me searching for the message.’ Sam nods her head at a shop assistant standing next to a forest of standard lamps. He’s staring at us with his eyes narrowed. ‘I suppose it did look a bit suspicious, me lifting up every lamp.’

‘Yeah, he’s still watching us – let’s go.’ I take the light bulbs from Sam and walk a bit closer to the assistant. ‘No, she didn’t want these,’ I say loudly. ‘She said she’d already got them online. Don’t you remember?’

Sam tucks away a smile before answering me equally loudly. ‘Oh, that’s right, I forgot! Stupid me!’ She watches as I put the light bulbs back and then tugs on my sleeve. ‘We’d better go meet her. You know how mad Mum gets when we’re late.’ We walk away towards the escalators at a quick pace.

‘Do you think he’s following us?’ Sam says.

‘Shhh!’ I pull out some glasses from my bag. They’re clear glass with tiny mirrors attached to the sides so I can see behind me. I can see the assistant looking after us but after a moment he shrugs and returns to the checkout. ‘No, he’s not following. But we’d better make sure no one else is.’

We make our way onto the escalators, going down to the first floor towards the café. As we get off at the bottom, Sam coughs twice – our signal to do the palm slip we’ve been practising for weeks. As she walks one pace ahead, she swings one hand behind her. I reach out and she presses the paper against my palm for a split second. In one quick move I clutch my fingers around it and tuck it away in the pocket of my dress (Dad finally listened to me about my need for pockets). Then I fake a sneeze, our signal to split up to confuse anyone who might be following us.

Checking there’s no one around, I slip into the women’s loos and find a cubicle to lock myself into. I take out the message and check it – it’s in code, of course, and I don’t have the cipher with me in case both message and cipher are stolen. Mum and Dad’s top spying motto is ‘Attention, attention, attention.’ (Their motto is exactly as irritating as it sounds.) So I pull out my phone and take a photograph of the code, then send it to Mission Control at home. Then I tear the paper into tiny strips and flush them down the toilet. Before I leave I change into another dress I’ve packed in my bag, this one in bright red, and put on a matching beret pulled down low over my eyes. Finally, I empty out my bag and turn it inside out – it’s a reversible rucksack with different colours on each side – before putting everything back. Mum and Dad have said that if you’re being followed and you change your clothes for something more striking, then the person tailing you will often reject the possibility it could be you. Let’s hope they’re right, because apparently HQ think the results of our training missions are almost as important as our real ones.

Coming out of the toilets, I try to change my walk, hunching my shoulders forward, and tilting my head slightly to the side – but not too much in case I just look weird. There’s a man wearing sunglasses and a large hat sitting right at the edge of the café, his face hidden by the newspaper he’s reading. He glances up over the edge of his paper as I come out of the toilets. Trouble. I make a swift left and push through the door that leads to the main stairs and lifts. As soon as I’m out of sight of the man I run down one flight of stairs and go into the household goods department. I weave my way through the aisles of cereal bowls and the cooking tools that look like instruments of torture. As I duck behind a display of bone china mugs, I think of the best spy of all time, Dan McGuire. In Dan McGuire and the Case of the Chipped China, Dan McGuire has to run through a factory of four thousand china plates without breaking anything. Now I know how he felt. A tall woman in a hat is cruising the aisles – she might be looking for more than a lemon squeezer. Well, you’re not going to squeeze me, lady.

I bend down, pretending to pick up something off the bottom shelf and then stay down as I scuttle into another aisle and over to the doors on the other side. I slip out and then down the steps to the fire escape doors to the street. I glance behind me. No one. I walk quickly towards the meeting point Sam and I had agreed upon – a café around the corner from the department store. I see Sam waiting and, right behind her, the enemy spy! I spin round and step into the next doorway I see. I send her a text – ‘Boring!’ – our way of saying ‘danger’. I wait for sixty seconds and then peer out. The enemy spy is gone and so is Sam – she must have followed our back-up plan of returning to base separately. I hope she manages to shake him off otherwise we’ll fail our test.

I take three buses instead of one to be sure there’s no one else tailing me. When I get home I go straight to Mission Control, Mum and Dad’s secret spy office hidden behind a cupboard door in the kitchen. I tap the code into the panel to make the door slide open, and walk in. Mission Control is one of the best things about having spy parents. Some parents have a secret chocolate or crisp drawer. My mum and dad have a secret spy room. Every wall is covered with screens, panels with buttons and slots for gadgets, and the whole place is stuffed with more hi-tech gear than a James Bond film set. Mum and Sam are there along with the enemy spy – Dad.

‘Well done!’ Dad says. ‘You passed that test with flying colours. HQ are really happy with how you’re coming on, especially with your disguises.’

Mum holds up her phone, smiling. ‘Yes, they were particularly impressed with the way you prevented anyone from stealing the code before it was deciphered. And you used a lot of other spy techniques too.’

‘Change of location, change of appearance, change of accessories, quick message exchange, warning your partner about being followed,’ Dad ticks everything off on his fingers. ‘Really, it was textbook stuff, Josie.’

I wince at the name. Dad always tries to call me Josie, even when we’re at home, so that none of us make a slip-up when we’re in public. But it’s like listening to nails down a chalkboard.

‘Yeah, you were great,’ said Sam. ‘All I did was get followed by the “enemy” and almost be caught by that shop assistant!’

‘That’s not true,’ I tell her, ‘you’re the one who found the code.’

‘Admit it, the best spy won and that was you,’ Sam says, grinning at me. ‘But we do make a good team.’

‘No. We make a blinding team,’ I tell her.

It wasn’t that long ago that it felt like Sam was better at everything than me. And okay, she’s still better at football, but at least now I feel like we’re equal as spies.

‘We have some other good news for you too,’ Dad says.

‘We’ve got a new mission?’ Sam and I have been hoping for a new mission from HQ for a few weeks now – we can’t wait. The training exercises are fun, but it’s not the same as the real thing.

Dad’s smile gets wider. ‘Well, yes, but that’s not the good news I’m thinking of.’ He scratches his stubbly chin and raises his eyebrow, clearly thinking he’s 007.

He takes a breath to go on but before he can speak, Mum breaks in. ‘You’re going to be a boy again.’

Dad makes a grumpy humph sound. ‘I was going to say that!’

‘You always take too long,’ Mum says with a shrug.

‘I don’t care who says it – do you really mean it?’ I switch my stare from one to the other for any signs that they’re having me on.

Dad rushes to speak before Mum can say anything. ‘Yes. As soon as the mission is finished, then we’ll be moving on to somewhere you can be a boy. Though you might not be able to go back to being called Joe.’

‘I don’t care if I’m called Rumpelstiltskin if I don’t have to wear dresses any more!’ I can’t stop smiling. This is the best news ever.

‘We’ll have to move quite far away,’ Mum says, her expression turning serious.

‘Fine, fine, let’s move to Brazil! Anywhere! As long as I can be a boy again!’

And then I catch sight of Sam’s face.

Oh.

‘Ah,’ Dad says, catching sight of our expressions. ‘Yes, it’s true that there’s a downside to this. Moving will mean we have to cut ties with everyone from our current life.’

So if I go back to being a boy that means no more missions together. No more best friend. No more Sam.

Why is it that every time Mum and Dad give me good news it turns out to be bad?