"What's wrong?" asked Lucy-Ann as the boys ran back to them.

"I don't think Rob and his friend are too happy about missing their flight," said Philip. "Run, we must find somewhere to hide." They all ran full pelt up the hill and then they heard to their dismay the sound of a car revving up.

"They are going to come after us in the car," said Jack. "We will never be able to outrun them."

"Head back towards the aerodrome," said Dinah quickly changing direction to the right. "We would be trapped if we went back to the shed." The others agreed and ran in and out of the trees, hearing the sound of the approaching car drawing nearer.

"Quick, shin up a tree," said Jack. "Hopefully they will pass and give us some time to get away." They all scrambled up trees and sat still, peering down between the leaves when the car drew closer. Luckily it didn't stop under the trees but carried on up the hill.

"Come on quick now," said Philip. "Let's go and find somewhere to hide while they are gone." They climbed down from their trees and ran down towards the aerodrome. As they were nearing the side of the building the sound of the car came to their ears again.

"Hurry," cried Lucy-Ann as the car appeared round the corner. The men in the car saw them and started shouting and sped up the car.

"Send for the doctor, pussy's down the well," chimed in Kiki.

"Yes Kiki," said Jack. "But be quiet now."

"Down here," called Dinah indicating a little passage to the right of the building. They all quickly raced down the passage with the car only a few metres behind them. Then the sound of the car died and they all glanced over their shoulders. The car had been too big to fit down the little gap. The men had stopped the car and were getting out. They had decided to go after the children on foot. They ran along the passage and found themselves outside a set of doors. Without stopping to think whether there might be anyone inside, Philip wrenched open the doors and they all ran through them. They found themselves on the ground floor of the aerodrome that was now deserted of any planes.

"What are we going to do?" asked Dinah. "There is no where to hide in here."

"Quick, head to those steps over there," said Jack indicating a set of metal stairs in one corner. They all ran towards them and raced up them.

"Carry on up," said Philip who was at the back of the group. "Go as high as you can." Dinah who was leading went up another two flights of stairs before they reached the top. Just as they did they heard the door on the ground floor being opened and the two men rushed in and they all froze. The men started to search the ground floor, but soon began looking upwards.

"Take off your shoes," Jack mouthed silently to everyone. "They make too much noise." They all quietly slipped off their shoes and then ran along the pathway that led right around the top of the building. They made no noise, and soon came to a room, built up against the wall. They stopped outside, debating whether or not to go inside when they heard the sound of the men running up the metal staircases, so Jack cautiously listened against the door before trying the handle. It opened and they went in. The room was very dark after the brightness of outside and completely deserted.

"No one switch on the lights," said Jack. "The glow would be seen."

"I'll just get out my torch," said Philip. "But I'll put my hand over the beam." He did this and in the dim light they were able to make out a sort of storeroom. They were crates of water stacked against one wall with tins of soup, veg and fruits against another and even more things which they didn't stop to look at.

"This is no good," said Lucy-Ann beginning to feel panicky. "There is no where to hide in here."

"There isn't even a lock on the door," said Dinah. "Now we are trapped in here. If we go out again we are sure to be seen and if we stay still we are bound to be found." She slumped against a huge sack of flour feeling dejected. The boys looked around wondering what to do.

"I don't suppose we could hit them over the head with a huge bag of flour, could we," asked Jack, even though he didn't really expect it to work.

"I'm not sure," said Philip. "They do look jolly heavy. See if you can help me life one Jack." The two boys tried and failed to life one of the huge bags.

"Oh it's useless," said Dinah beginning to feel stressed herself. "Why don't we just go and hand ourselves over to the men, and save them the hassle." The two boys stopped what they were doing and turned to stare in amazement at Dinah.

"Dinah!" exclaimed Philip. "What on earth's the matter, you've never wanted to give up before."

"I know," said Dinah. "I don't really meant it. It's just that I'm tired and stressed and worried about Bill and…"

"Hey! Look a vent!" cried Lucy-Ann interrupting. "Maybe we could hide out in there."

"Where? Oh yes it looks just big enough for us to crawl into," said Jack. "Philip give me a boost up to it and I'll see if I can get it open." Jack was boosted up to the vent and pulled at it. It didn't budge and he saw two screws, at the top corners securing it. He got out his penknife and used the blade to turn the screws. They came out quite easily and he pocketed them. He removed the grate and placed it just inside the vent.

"I'll see if it's big enough to get into," said Jack. He then heaved himself up and disappeared. He soon came back and gestured to the others to come up. Lucy-Ann went next and was helped in the vent by Philip. Dinah followed her, hearing the men's footsteps approach on the metal walkway. Philip had to jump and grab onto the edge of the vent and then Jack helped to heave him up.

"Place the grate over the vent," said Dinah and Jack refitted the grate, which they had to stick into place with some blue tack, as it was impossible to put the screws back in.

"I hope it doesn't fall down," said Philip.

"I don't like this," said Lucy-Ann. "It's cold and dark in here."

"I suggest we follow this vent and see where it leads to," said Jack. "We could possibly escape through somewhere else." The others agreed, except Lucy-Ann who was rather afraid of the dark vent. But she didn't want to be left behind, so she follow after the others They crawled silently away from the room on their hands and knees, feeling the cold metal ridges of the vent around them on all sides. When they had only gone few metres they heard the sound of the men entering the room. The vent was slightly lit up as the men turned on the light and from the sound of the crashes and thumps that floated along the passage the men were angry and intent on finding them. They carried on crawling and gradually the noise died.

"I think it would be safe to switch on my torch now," said Philip. "I don't like not being able to see where I am going." They all felt much more cheerful when the torch's light shone through the passage.

"That's better," said Lucy-Ann. "I don't feel I could fall down a hole at any moment now."

"That's silly," said Philip. "I'm before you, and for you to fall down a hole, I would have to fall down it first."

"I can't help what I think," said Lucy-Ann.

"Can we carry on please," asked Dinah. "I don't like being so closely surrounded on all sides."

"Okay," said Philip. "The sooner we get out of the here the better." They carried on wondering how far they would have to travel before they could get out.

"I wonder how Bill's getting on," said Dinah. "I hope he's alright."

"I'm sure he is," said Jack. "We know better than anyone that Bill can look after himself." They had been crawling for nearly twenty minutes when Philip suddenly came to a stop.

"What's the matter?" asked Jack.

"The passage splits into two here," said Philip. "Do we go to the left or the right?"

"Left?" suggested Dinah. "It doesn't really matter, does it, as long as we're heading away from those men."

Philip carried on crawling. All their knees were feeling quite sore by now. As they crawled on, a whirring noise became louder and louder. Soon, Philip saw what it was ahead: a fan, spinning round in the wall of the vent, obviously helping to circulate the air, which was what the vents were for in the first place.

Philip made to go past it, but Lucy-Ann grabbed his ankle. "Philip, don't! I don't like it!"

"It's not going to hurt you," said Philip, mildly amused.

"I don't like it!" cried Lucy-Ann. "It might suck you in, it's dangerous!"

"Don't be silly," said Dinah impatiently from behind her. "Hurry up, I want to get out of here."

"It'll be all right, Lucy-Ann," said Jack.

Philip crawled forward past the fan. "See?" he said. "It's not powerful enough to suck you in."

Lucy-Ann took a deep breath, and moved forwards. The others all followed. About ten minutes later Philip stopped again.

"What now?" said Jack exasperatedly from the back.

"Shh!" said Philip. "I've reached another grate. It leads into a room. Be quiet, there might be people around."

"What are we going to do?" asked Dinah, fed up of being forced to stay on her hands and knees.

"I'm just listening to see if anyone seems to be nearby," Philip hissed back. "I can't hear if you are talking!"

"Well, I can't hear anyone-" began Dinah, but stopped as Lucy-Ann kicked her.

They could all hear the sound of a door opening, and Philip could see through the gaps in the vent that the door to the room beyond had opened. Rob entered, but then Philip heard the voice of his friend call out. "We've looked in there. Come on, they've gone, must have gotten outside."

Rob took a last look around the room. "Yeah, all right," he said, though he didn't sound happy about it. He left, and the door closed.

Philip breathed a sigh of relief. That had been a little closer than he would have preferred. He was sure that Rob could have seen him if he had looked straight at the grate. "Did you hear that?" he called back over his shoulder. The others answered yes.

"I'm going to try and push the grate out," Philip said. "Can you back-up a bit to give me some room?"

The other three shifted backwards in the vent. Philip backed up a bit too, then swung at the grate with his shoulder. To his surprise, it fell out easily, and he nearly fell into the room after it. All of the children held their breath in case the men had heard and came back, but after five minutes no one had come, and they felt safe.

Philip climbed stiffly out of the vent and dropped to the ground, then he turned round and helped Lucy-Ann and Dinah down. Kiki flew into the room with a shriek of delight at being out of the vent. She had ridden on Jack's shoulder but hadn't liked it one bit. Jack jumped down beside them, and he and Philip wrestled the grate back over the vent to cover their tracks.

The room looked like a staff room of sorts. It had a few comfy chairs scattered around, and a sink and kettle in one corner. A thin red rug lay in the middle of the floor. Dinah looked in the cupboard under the sink and found some biscuits, which they took eagerly, as it had been a while since their last meal.

"In fact, I don't think we've had a proper meal for days!" said Lucy-Ann.

"I think the vent must come all the way round the building," Philip guessed. "I bet this door opens onto the metal walkway." He opened it a crack and had a look out. "Yes," he said, shutting it again. "The room we entered the vent from is the other side of the hangar now. We've crawled a long way!"

Jack brushed some biscuit crumbs off his front. "Right, what should we do then?" he asked. "Stay here? Or try and get back to the shed?"

"We don't know where Rob and his friend are now," said Philip. "We could be seen if we go back out."

"But if we stay here they might decide to come in here any minute," said Dinah.

"True," mused Jack. "But I don't want to hide in that vent any more. It's horrible in there."

"We ought to go out, surely?" said Lucy-Ann. "Otherwise Bill's friends might not realise that there are other people here and they might get into trouble. They are expecting us to be in the shed."

"Don't worry about that," said Jack. "They are trained to be careful. Anyway, I'm sure Bill told them what he was doing, and explained that another pilot was turning up."

"I suppose," said Lucy-Ann. "I wonder who will come. Is he still working with the same people who helped us when we were trapped in that castle? I liked them."

"I've no idea," said Philip. "You know Bill never talks about his work."

"Silly Billy, silly Billy!" cried Kiki, from Jack's shoulder. Jack reached up and stroked her feathers, feeding her a crumb of biscuit.

"I wish he would," he said. "I'd be very interested to hear all about it. I wonder how you get into that line of work. I'd like to do that when I get older."

"Me too," said Philip fervently.

"Shh!" said Dinah suddenly. They looked at her in surprise. "Did you hear that?" she whispered.

They shook their heads. "What?" whispered Jack.

"It sounded like a footstep outside the door," said Dinah, looking scared.

They listened intently, and froze as they heard the sound of movement, clearly audible due to the walkway outside the door being made of metal.

Someone was sneaking up on them.

"Vent?" whispered Dinah.

"No time!" hissed Philip. "You girls get behind that chair. Jack, help me pick up this rug on the floor. When the person comes in, we'll throw it over them. Girls, you run when we've done that, okay?"

Dinah and Lucy-Ann were already behind the chair, hidden by its tall back. Jack and Philip picked up the rug and stood beside the door. Their hearts were beating fast. They heard another slow step on the walkway. Then, the door handle moved, almost imperceptibly, as someone placed their hand on it. "Ready?" breathed Jack. Philip nodded, raising the rug higher.

Suddenly, making them all jump even though they were expecting it, the door burst open. Jack and Philip threw the rug over the person, and pushed him hard. He fell over backwards out of the room with a shout. "Run!" yelled Philip, and the girls sprinted out from behind the chair, out of the room, and turned left. Philip followed, but the rug-covered man was starting to get to his feet, blocking the way and so Jack ran to the right.

This soon turned out to be a mistake though, as a hand shot out of nowhere and grabbed his arm in a vice-like grip. "Let me go!" shouted Jack, hitting out at his captor with his free arm.

"Steady, steady," said a quiet voice. "Calm down, it's okay!" Jack looked up, and realised that the man wasn't Rob or his friend. In fact, he looked vaguely familiar.

"Bill's sent me," said the man with a smile. "I'm Jim." Philip, Dinah and Lucy-Ann had stopped their flight at the top of the stairs leading downwards.

They slowly came back over.

"Jim!" cried Jack. "I'm sorry, I didn't recognise you, I mean, I didn't have time to look, and you were wearing dark paint when I met you before. You look different," he finished lamely. The man who had been attacked with the rug had finally got himself free. Philip noticed that he had a revolver in one hand, and thought privately that it had been lucky the man hadn't fired blindly when they had attacked him.

He looked a little ruffled, but introduced himself as Tom. The children had met him before too.

"There's at least two men about," Jack informed them quickly. "One's called Rob. We don't know what the other one is called."

"Don't worry," said Jim. "We've got them already, they are handcuffed in the back of our van. We found them in the hangar, but they told us there were ten other men all armed, so we were being careful!"

"We haven't seen anyone else," said Lucy-Ann, confused.

"No, I think they were just trying to scare us off!" said Tom. "Are you all all right?"

"Yes, we're fine," said Philip.

"Good, we'd better get going then," said Tom. He led them downstairs and out of the door. The children saw about five policemen standing around.

"They are here to guard the hangar until we get back, to make sure no one comes and tampers with any evidence," Jim explained. "They'll also take Rob and his friend to the police station." Tom and Jim led them to a large silver car, and the children squeezed in the back.

As they sped off down the hill, Jim explained that they were going to meet Bill. The children looked at one another excitedly. They thought that they had been going to miss out on that part of the adventure, but it seemed as if Tom and Jim wanted to be there to see Big Charlie being arrested as much as they did. "He's been flying round in wide circles to make Charlie think that they are flying a great distance, but they are actually going to land in an airfield not far from here. There's a big team waiting on the ground to apprehend him."

"You'll have to stay at a distance though," warned Tom. "We think it's all going well so far, though we can't talk to Bill over the radio because Charlie could hear too. We're just worried that Charlie might try something when he sees that Bill is landing and they are still in England."

The children exchanged worried looks. They had thought Bill was safe, but of course Big Charlie probably still had a gun on him. Philip hoped that Bill had taken those sleeping pills with him and had managed to put Charlie to sleep. The car sped on. Soon, Tom turned round to face the children. "Almost there," he said with a grin.

The children all started to feel excited and looked out of the windows to try and spot the airfield. In five minutes time it came into sight. It was a long stretch of runway with a building at one end. It was surrounded on all sides by high wire fence and there was an armed man standing at the gates to the airfield. They drove up to the gates and Tom wound down the window.

"Green umbrella." The man on the gates nodded and pressed a button beside him and the gates swung open.

"What was all that about?" asked Philip as they drove through.

"Oh that was just to tell him we are part of the mission that's going on here."

"You mean a password?" asked Lucy-Ann.

"Yes, in a way. It was our operation name," said Tom. They drove over the airfield and parked next to another vehicle, which had more men standing beside it. They all climbed out and were introduced to the rest of Bills men.

"This is David, Gordon and Vince," said Jim. The children all shook hands politely and told the men how they had disguised Bill and how he had flown off with Charlie. Kiki wanted her part in the conversation too. "Where's your handkerchief, don't sniff," she sternly told a surprised Vince, who wasn't sure whether to answer her or not. Kiki strutted on Jack's shoulder at the admiring looks she received.

"Let's just hope there's no trouble," said Gordon.

"Right then men," said Tom, who had taken charge. "Gordon, David you go and stand next to the runway and guide the plane into landing. Vince, you stand in front of the building and Jim and I will be in the building waiting with the plane steps until they land. Right, when they land we act natural. Jim and I will wheel out the steps and hopefully Charlie will climb out before he realises where he is. When he does, I want Gordon and David to cover him and try and get him to drop his gun. Vince, I want you to try and get behind the plane in order to take him by surprise if the need arises. All agreed… right, let's get going then."

"What are we going to do?" asked Jack. "We want to have a part in all of this too."

"You lot can either hide in the trees around the edge, or go into the building and look out of one of the windows," said Tom. They were all hoping for a bit more involvement than this, but decided not to argue, as these men clearly knew what they were doing. In the end they decided to go and hide in the trees, at least they would be outside then and might get the chance to hear what was being said.

"When is Bill planning to land the plane?" asked Dinah.

"Anytime soon. After he has made one more circle."

"I hope everything has gone all right," said Jack.

"I'm sure it has, now go and hide in those trees," said Jim. "I think I can hear the plane approaching." They all ran to the trees and hid behind them eagerly. Tom and Jim disappeared inside the hanger and David and Gordon ran forward with little paddles to guide the plane into land.

"Here it comes," said Lucy-Ann feeling excited. They all watched as the plane started to descend, guided by Gordon and David.

"There go the wheels," said Philip. "Now all he has to do is touchdown."

"I hope it all went okay," said Lucy-Ann.

"Well we'll soon find out," said Jack. David and Gordon ran off to the sides, just as the plane touched the runway. It gave a jolt as it touched down and then ran a few yards before turning slowly coming to a stop.

"This is it," said Philip feeling tense. Jim and Tom came out looking perfectly relaxed and wheeled the steps up to the door of the plane. They made sure they were fastened and then stood back and signalled to the front of the plane that everything was set for them to come out. Everyone held their breath as the door was opened. The moustached, bearded, sunglassed, Pilot Bill came into view. He grinned and gave a salute and then stood back.

"Oh good, Bill's alright," said Jack. Big Charlie came to the door and stepped outside onto the top of the stairs, he took a step down and then stopped and looked around him in surprise. Gordon and David, sensing his suspicion, ran forward and drew their guns. Charlie saw them and instantly sussed what was going on, as he realised they were still in England. He quickly turned and jumped back inside the plane. Tom and Jim also drew their guns, but Charlie was already back inside the plane.

"What's happened?" asked Lucy-Ann nervously. "Has it all gone wrong?"

"I'm not sure," said Philip. "Let's just watch." Just then Bill appeared at the door again. Bill didn't have his sunglasses on and he had his hands in the air and looked worried. They saw to their horror that Charlie was covering Bill with his gun.

"Oh no," cried Dinah in dismay. "It's all gone wrong, Charlie's got Bill!"