On Thursday that week, a visitor came into school. The headmaster introduced him in assembly as Mr Lucas, a member of the St John's Ambulance. He would be going around each of their classes to teach them some basic first aid.

He showed Miss Broom's class how to bandage someone's head. He was using Emma to demonstrate until Des whispered into her ear that Mr Lucas was turning her into a mummy. Emma then tore off the bandage and ran to Miss Broom. Miss Broom scolded Des, apologised to Mr Lucas and then asked him to continue.

Both Charlie and Anna watched fascinated as Mr Lucas used demonstrated how to handle a broken bone, using Des as his model this time. He used a strip of wood called a splint, which he fastened to Des's leg firmly with another bandage. This, he explained, kept the bones still, but Des had already pulled the splint out and was using it as a sword against those in the front row.

It was Friday before Des pounced.

He cornered Charlie in the cloakroom and pinned him against the wall.

"You didn't scare us, freak," he growled. "We were leaving already, got it?"

Charlie just nodded.

He could see Roger hiding behind two coats on hooks and Sam was crouching behind the large metal wastepaper bin. The door to the supply cupboard was ajar, so Eric was probably in there. Des had others to back him up. Charlie didn't.

"We didn't even see you until we were out the gate," Des boasted.

Charlie nodded again. He didn't feel the need to argue. He knew he had scared them off, and more importantly, he knew that they knew he had scared them off. Des was kidding no one.

"Tomorrow. 0900 hours. The park," said Des sharply.

Charlie raised an eyebrow. Des poked him in the chest.

"Be there," he said. "Unless you're scared..."

Charlie shook his head. "We'll be there," he muttered.

Des let go of Charlie and took a step back. He tried to stare Charlie out, but Charlie was better at that game and Des lost. He turned round and stormed off scowling. Charlie watched him go. He looked over to the coats. There was definitely someone hiding behind them.

He grinned, then went off to find Anna.

Both Charlie and Anna were at Fort Freak with thirty minutes to spare that Saturday morning. By this time they knew what Des was planning and had come prepared. They both wore their waterproof cagouls, done up to the neck.

Anna, however, was more concerned about their weapons.

"We'll be no match," she sighed, looking over their arsenal with disdain.

Charlie had brought a puny little water pistol, but the trigger was snapped off and the water was leaking out anyway. Anna, on the other hand, had made some smoke bombs out of small paper bags and flour, but these had broken in her bag on the walk over.

"We've still got the pea shooter," Charlie said.

He had found an old pea shooter at home and had pinched a bag of frozen peas from the freezer as he came out. However, when he opened them up he found they had thawed and gone all mushy. He tried firing one, but it got stuck in the end of the pea shooter instead.

"Useless," muttered Anna. "Completely useless."

Shortly before nine, Charlie clambered up the tree and settled amongst its higher branches once again. Looking out across the park he found it to be almost entirely empty. There were several dogs being taken for early morning walks, and a jogger out on a run. The park was so empty that a flock of seagulls had settled on the football field. There was no sign of Des and his gang.

"Nothing," Charlie reported as he climbed back down the tree.

Anna was trying to scoop the flour back into the paper bags but was not meeting with much success. The paper tore open in her hands and she threw the bags down in disgust. A small cloud of flour rose around them; it really did look like a smoke bomb!

"That's it," she decided. "Let's call this thing off."

Charlie frowned. "But we'll look like chickens," he moaned.

"I don't care," said Anna, beginning to pout.

Suddenly there was an awful racket over on the football field and the two of them leapt up to see what it was. All those seagulls that had been resting there a moment before had suddenly taken to the air and were flying away. Charlie spotted what had startled them and groaned.

The figures of four little boys were romping across the field.

"Des?" said Anna quietly.

Charlie was wearing the binoculars around his neck. He looked through them.

"Des," he confirmed.

The four boys were tearing across the football field in the direction of the children's playground. They wore dark clothes and had camouflage paint on their faces. They looked ready for war.

Anna sighed. "Come on, then," she said. "Let's call a truce."

Charlie nodded, though honestly he wasn't so sure. A war seemed like fun.

Anna started to weave her way through the bushes and Charlie followed at her heels. She led the way to the playground silently. It was completely deserted, which Charlie had never seen before. He could hear the swings creaking as they swung gently back and forth.

They stopped at the gate and looked around. There was no sign of Des.

"Where are they?" whispered Charlie, wary that they might be near.

Anna shrugged. "Hiding?" she whispered back.

"Maybe we should call out..." Charlie suggested.

Anna shook her head.

Instead she gestured for them to spread out and search. She made her way slowly toward the climbing frame. Charlie crept toward the slide. There weren't many places in which the enemy could be hiding, and those that there were, like the slide, would not hide all four.

Charlie peered carefully behind the slide. There was no one there. It was right on the edge of the playground and behind it was a fence that kept loose dogs away from the children. Beyond the gate was a grove of ancient trees.

Charlie was looking the wrong way. He didn't see Des appear from behind one such tree and lob a water bomb over the fence. It hit Charlie in the face and exploded, drenching him instantly. Charlie leapt in the air and yelped.

"Wa-wa-wa-wa-wa!" Des gave a war cry and tore off into the trees.

Anna came running up.

"Oh, Charlie!" she said.

In the end his cagoul had been useless. His hair was soaked and water had run down his neck and inside his jacket. He was dripping all over the grass. They heard Des give another war cry as he ran and this time they heard three other war cries echo back from deeper within the grove.

Charlie growled and swung open the gate in the fence.

"Come on!" he barked, charging through. "We have to get them!"

Anna chased through after him, but Des had a head start. He had stopped on the other side of the trees to taunt them with rude gestures and catcalls. His three henchmen were nowhere to be seen.

"Des!" they called, but he just started running again.

Charlie started after him once more, but Anna caught his arm.

"He thinks we're chasing him," she explained. "We have to find another way."

Charlie thought for a moment, then nodded, so they started picking their way through the grove slowly and quietly, hoping to sneak up on Des when they reached the other side.

The grove was quite a dark and scary place. The trees creaked spookily all around and dead leaves crackled underfoot. The wind passing through the trees sounded like eerie whispers. When Anna grabbed Charlie's arm again, he jumped.

"W-what?" he said.

She pulled him behind the nearest tree and they stood there hidden for several seconds. Then she leant out sideways and pointed at something in the trees. Charlie couldn't see anything at first, but then he saw the figure in the trees.

It was Eric.

There was a dead tree up ahead and he was trying to climb higher and higher. Thought it looked an easy climb to Charlie, Eric was finding it difficult because he was holding a carrier bag in one hand.

"Eric!" shouted Anna.

She leapt out from behind the tree and charged forward. Charlie followed.

Eric saw them coming from afar and let out a startled gasp. He suddenly slipped and was left hanging by his hands. Both feet flailed in the air as he fought to regain his footing, but then he managed to steady himself and looked round.

"Eric!" cried Anna again, bounding through the undergrowth.

But then Eric did something Charlie thought incredibly stupid.

He let go of the tree.

He was trying to reach a water bomb from the bag, but to do this he needed both hands. He pressed himself up against the trunk, his feet resting on knots in the wood and supporting his entire weight.

"No, Eric, don't!" Anna yelled, but it was too late.

One foot gave way and he came crashing to the ground. He landed heavily on his arm and cried out in pain. Charlie and Anna froze before him.

"Oh, Eric," gasped Anna.

Charlie was in shock. He could do nothing but watch Eric squirm and whimper beneath the tree.

Suddenly Roger and Sam appeared from nowhere and began showering Charlie and Anna with their water guns.

"Stop it!" screamed Anna, grabbing at Roger's gun. "Look!"

Roger and Sam spotted Eric sitting up at the base of the tree, cradling his arm.

"W-what... happened?!" cried Sam.

"He fell out of the tree," Anna said.

"It hurts..." Eric sobbed.

They all crowded round anxiously. Nobody knew what to do. Anna crouched down beside Eric and he tried pushing her away. That just hurt his arm all the more and he winced loudly.

"I think he's broken his arm," Anna told them, rising to her feet again.

There was a sudden war cry and Des leapt into the clearing with a water bomb in each hand and a balaclava on his head. He was ready to drench Charlie and Anna, but Roger leapt into his way.

"Stop it!" he demanded. "Eric's hurt his arm!"

Des forced his way to the front but stopped when he saw Eric blubbering.

"You did this, freak!" he snapped, turning on Charlie and shoving him.

"Did not!" Charlie hollered, pushing Des back.

There was uproar. Anna leapt to Charlie's defence. Sam leapt to Des's defence. Roger shouted for them all to shut up but nobody listened. They only fell silent again when Eric let out a loud bellow.

They all stopped pushing and shoving each other and looked at Eric.

"It was an accident!" Eric insisted. "An accident."

Nobody moved or said anything. It was Anna who took the initiative.

"We need to find a splint," she decided.

"A what?" Des grunted.

"A straight piece of wood," Anna replied.

Charlie had finally calmed down now.

"Here," he said, finding a dry old stick in the grass. "What about this?"

"It's too long," she said.

"Let me," said Sam, taking the stick from Charlie and snapping it in two.

"Thanks," Anna said, taking the longer piece.

She knelt before Eric and paused.

"I need a belt, or laces, or something like that to tie it to his arm," she said.

The boys looked around blankly. None of them were wearing belts and they all wore either plimsolls or velcro trainers.

"Somebody must have something," Anna cried desperately.

Eric winced again.

"It hurts so much," he moaned. "Go get help!"

Roger stepped forward.

"I'm the fastest runner," he said. "I'll go."

Anna nodded. Charlie also agreed. He had seen Roger run on his first day at school and remembered how speedy he was. Roger broke into a run and Charlie watched him go. He was soon out of sight.

"We still need something to hold this splint in place," Anna said.

She looked around but she found nothing. Her eyes settled upon Charlie. Des and Sam also came to same conclusion, but Charlie did not. Even Eric was staring up at him through his tears, and in that instant it came to him.

"My... tail?" he whispered.

Anna nodded.

"Please..." Eric pleaded.

Charlie didn't think about it. Had he done so, he would never have done it. So he did not think about it, and he did do it. He knelt down at the foot of the tree, with his back to Eric. He slipped his tail out of his trousers and coiled it gently but firmly around Eric's arm and the splint.

Eric winced at first, but then he stopped crying and sat quietly.

Charlie glanced round over his shoulder. Eric already looked more comfortable. Anna was squatting on the other side and smiling proudly at him. Des and Sam stood there watching in an amazed silence.

"Thanks," Eric muttered. "Thanks a lot."

It wasn't long before Roger returned with an ambulance crew. Charlie was dreading what they'd have to say about his tail but in the end they did not say anything. They simply uncoiled it and applied a proper splint and bandage. Then they put Eric's arm in a sling and helped him to his feet.

The five of them followed Eric to the ambulance, which was parked on the other side of the playground. A large group of people had gathered to see what all the excitement was about. Eric was lifted into the ambulance and the doors were closed.

As one of the paramedics got into the driver's seat, another turned to them.

"You've all done exceptionally well," she told them. "Well done."

Charlie felt a warm glow inside. Anna was blushing proudly and even Des couldn't help himself but break out into a huge grin. Eric appeared at the window in the back of the ambulance and waved.

"He's very lucky to have such good friends," the woman added.

Then she climbed into the ambulance and the engine was started. The five children stood side by side and watched as the ambulance slipped through the park gate and disappeared out of sight.