“Look, we’ve got to decide what we’re going to do,” Frankie said, for about the zillionth time. “If we don’t get our own back, the M&Ms’ll never let us forget it.”

We all nodded, but none of us said anything. We were too depressed. We were sitting in Frankie’s back garden, the sun had started shining and we were eating pizza, but we were still miserable. That was because we couldn’t believe the nerve of the M&Ms.

“I still can’t believe they did it,” Lyndz said. “I mean, the M&Ms are so goody-goody and all that.”

“Yeah, I would’ve thought they’d be scared of getting caught,” Rosie agreed.

“Well, there wasn’t much chance of that, was there?” Frankie pointed out. “Mrs Weaver was in the book cupboard, and everyone else was watching Ryan and Danny fighting with the metre sticks.”

“And Emma was so close to the computer, she wouldn’t even have had to get out of her chair,” I said. “You know what I was really worried about? I thought Mrs Weaver might say I couldn’t come to the museum sleepover.”

“Yeah, you were lucky to get away with just a detention,” agreed Frankie.

We all sat gloomily looking down at our pizzas. Not even the thought of the museum sleepover could cheer us up at the moment.

“You should have told Mrs Weaver it wasn’t you, Kenny,” Fliss said, also for the zillionth time.

“I did, and she didn’t believe me,” I said impatiently.

“You could have told her it was the M&Ms,” Fliss persisted. That girl never knows when to give up. I glared at her.

“I’m not a snitcher!”

“Anyway, Mrs Weaver wouldn’t have believed you,” Frankie cut in quickly. Just in time to stop me throwing a half-eaten slice of pizza at Fliss.

After what had happened, I wouldn’t have got through the rest of the day if it hadn’t been for the others. The M&Ms were real pigs. They kept staring at me and giggling, and looking really smug and pleased with themselves, and they made me so angry, I could have gone over there and knocked their heads together. I think Frankie and the others were a bit worried I might actually do it, because they’d stuck to my side like glue all day.

“Come on, someone must have a really good idea for getting our revenge on the M&Ms,” Frankie said. “We’ve got to think of something.”

“What have Emily and Emma done now?” Frankie’s mum asked, coming towards us with a jug of lemonade. No-one had even noticed her come out of the house, and I wondered how much she’d overheard.

“Nothing!” we all said together. Well, all of us except Fliss.

“They played this really horrible trick on Kenny,” she said breathlessly. “What they did was, they – OW!”

Fliss was sitting between Frankie and Lyndz, so one of them must have kicked her leg. Quite hard, too, from the look on Fliss’s face. She turned pink, and shut up. I like Frankie’s mum a lot, but this wasn’t something we wanted to tell grown-ups about. This was private, Sleepover Club business.

Frankie’s mum raised her eyebrows and waited, but we all just looked innocently at her. We’re good at that. Well, Fliss goes bright red after about ten seconds, but the rest of us are brilliant at it.

I don’t think Mrs Thomas was fooled, though. But she didn’t say anything except, “Who wants some lemonade?” She filled our glasses, and then went back into the house.

“Who kicked me?” Fliss demanded crossly.

“Not me,” Frankie said innocently.

“Nor me,” said Lyndz, just as innocently.

Fliss looked from one to the other, and then gave it up as a bad job.

“I don’t see why we couldn’t have told Frankie’s mum what happened,” she grumbled, rubbing her shin.

“Because grown-ups just say things like ‘Oh, ignore them’,” said Frankie.

“Yeah, and they’d try to stop us getting our own back,” I said. “This is our problem, and we’ll decide what we’re going to do about it.”

“But we haven’t decided anything yet,” Rosie pointed out. We all sighed, and sat there in silence, sucking lemonade through our straws.

It wasn’t like I hadn’t thought about getting revenge on the M&Ms. In fact, I’d hardly thought about anything else all day. It would have been easy to ambush them in the girls’ loos, and chuck wet paper towels at them, or do something ordinary, like putting a fake tarantula on Emma’s chair. But that wouldn’t be good enough. They’d set me up and got me into big trouble – and I was going to get my own back in style. That meant some serious thinking.

But at the moment, with our faces as long as a wet week-end, we weren’t going to be able to decide on anything. It was time to get this sleepover going a bit. So I sucked some lemonade up through my straw, pointed it at Frankie and blew.

“Kenny!” Frankie spluttered, as lemonade squirted out all over her face. “You – you –! I’ll get you for that!”

She sucked up some lemonade furiously, and blew. I ducked, and it hit Lyndz instead.

“Ow!” Lyndz squealed. “It’s gone in my eye! It stings!”

To get her own back on Frankie, Lyndz began to suck some lemonade up her straw, too. But she sucked too hard, and began to choke. Rosie slapped her on the back, but a bit too much, and Lyndz pitched forward and got the straw stuck up her nose. The rest of us nearly died laughing.

I bet you can guess what happened next, can’t you?

“Now – hic – I’ve got hiccups!” Lyndz groaned, when she was finally able to speak. “Frankie – hic – help me!”

“Try drinking from the other side of your glass,” Fliss suggested. “That’s supposed to work.”

Lyndz picked up her glass, and turned it round.

“Like – hic – this, you mean?”

“No, dummy!” I said. “You hold the glass normally, but you try to drink from the opposite side.”

Lyndz bent forward and tried to take a sip, but she tipped the glass up too much, and ended up pouring lemonade all down her T-shirt. The rest of us cried with laughter.

“This is really stupid, Fliss!” Lyndz yelled, creasing up herself. “It’ll never work!”

“It already has!” said Fliss smugly.

“Come on,” I said, grabbing Frankie’s arm. “Let’s play one of our International Gladiators’ games on the lawn!”

Nobody mentioned the M&Ms and what had happened again for a long while after that. We had a few rounds of International Gladiators, then it started to rain so we went inside and played tapes and had a disco. Frankie’s mum let us make popcorn after all, and we scoffed two huge bowls of it while we watched a video.

We were all tucked up in bed before we got talking about getting revenge on the M&Ms again. Frankie was in her own bed, and me and Lyndz were in the bunks, me on top and Lyndz at the bottom. Fliss was in the camp bed, and Rosie was in her sleeping bag on the floor. Mrs Thomas said goodnight and turned the light off, then we waited a few minutes and switched our torches on.

“Are we eating first?” Lyndz asked, opening her sleepover bag, and pulling out a packet of chocolate digestives. “I’m starving.”

“No, wait a minute,” I said. “I’ve been thinking!”

“You probably want to lie down and have a rest then,” said Frankie.

“Ha, ha. No, I’ve been thinking about the M&Ms.”

“I’ve had an idea about that,” said Rosie. “Why don’t we do the same to them when it’s their turn to use the computer?”

“No, we’ve got to do something different,” Frankie insisted. “We don’t want to copy them.”

“We could hide Emma’s violin,” Lyndz suggested. “Then we won’t have to listen to her playing it in Assembly.”

“I think we ought to get them into trouble with Mrs Weaver somehow,” said Fliss. “After all, that’s what they did to Kenny.”

“What do you think, Kenny?” Frankie looked at me.

“I don’t think we should do anything,” I said.

The others looked shocked.

“What?” said Frankie. “Nothing at all?”

“No, I mean I don’t think we should do anything just yet.” I grinned at the others. “I think we should wait. Until the sleepover at the museum next week.”

Everyone looked puzzled.

“Why?” asked Lyndz.

I shrugged. “Think about it. There’s lots of spooky things in the museum, loads of places to hide and we’ll be there all night. We’re sure to be able to think of some way of getting our own back on the M&Ms while we’re there. And best of all –!”

“What?” said the others.

“Well, we’re excellent at sleepovers!” I pointed out. “We’ve been to loads. The M&Ms haven’t.”

“So we’ll be one up on them before we start,” said Frankie.

“We sure will!” I looked round at everyone, and we were all smiling. “The M&Ms are in for the biggest shock of their whole lives!”