It wasn't ordinary snoring. It could best be described as a combination of a hippopotamus with sinus trouble, an electric sander, a truck dumping a load of gravel, peak-hour traffic along a six-lane motorway and a dam bursting its banks.

Everyone sat up in bed saying polite things such as, 'Look, Abigail, do you mind…' and 'Abigail, sorry but do you realise…' But none of that had any effect and they started to bellow at her instead.

No luck. Abigail kept at it all night, bouncing out of bed in the morning glowing with health and rest. When the others gently mentioned the problem, she promised that she would try and restrain herself the following night.

Promises are all very well.

In fact, the next night she put on an astonishing performance, as though the previous night's snoring had just been a practice run.

'We can't go a whole week without sleep,' Natasha said desperately.

'We could try—' Laura said shyly but nobody heard.

'I'll just have to invent a special machine that cures snoring,' said Charlotte, who came from a long line of engineers.

When she had made her machine, Charlotte explained how it worked. 'I've sticky-taped a paper bag, open end down, on the wall just above Abigail's face. Above the bag there'll be a sheet of cardboard. Fixed to that will be a glove stuffed with something heavy so that it's like a boxing glove. Above the glove will be another board, and poised on one end will be a heavy object, like a boot. Just below the boot, on Abigail's bedside table, there will be a ruler balanced over a matchbox, and on the other end of the ruler, there'll be a bowl of water. And in the water, the thickest, soggiest sponge we can find.'

'Much easier to—' said Laura, but Charlotte and Natasha told her to shut up.

It was as though Abigail knew, even in her sleep, that some momentous experiment was taking place, for her snoring reached an astonishing crescendo. Very slowly the paper bag above her face began to swell. It billowed like a balloon and pushed against the cardboard shelf. The glove, stuffed with chocolate papers and socks, moved too. It rapped the board above, and the carefully balanced boot slipped off, as clean as an anchor. The boot then crashed down on the ruler edge. The saucer of water and the sponge jumped into the air and landed with a wet splosh right in Abigail Martin's face.

'Zzzzzzzzzz,' she said, without even flickering an eyelash.

'I'll ring my Mum and get her to come and pick me up,' Charlotte said, sniffing. 'I'm not going to miss a whole week's sleep.'

'Nor me,' said Natasha. 'Is there room for my things in your Mum's car?'

'I don't want to go home yet and miss camp,' Laura said. 'Anyhow, I think I can—'

'Why don't you just shut up for once,' Natasha said indignantly.

'—stop Abigail snoring,' Laura finished. She stood on her bed and gently turned Abigail Martin off her back and on to her side.

'There,' Laura said into the sudden calm of the snoreless room. 'That's how you stop people snoring.'