‘I’m not sure about this.’

‘Oh for God’s sake, this is a waste of time.’ Freak walked to the water’s edge, holding his nose. Deke groaned as he watched his friend wade in. Soon the slime was up to Freak’s knees, then his thighs. He carried on until he had reached the machine. Turned to wave, then peered inside.

‘Sick!’ he said, grinning. ‘You should see this.’

‘Freak! No!’ Deke screamed.

The whole surface of the water around Freak had come alive as if some huge beast was rising from the depths.

Deke splashed into the pool, yelling.

‘Idiot,’ said Achilleus.

There were shapes emerging everywhere now, seemingly made from the same green slime as the water itself. They pushed up out of the bubbling pool.

People. Men and women. Blanket weed hanging off them and tangled between their outstretched fingers like webs.

‘GROWN-UPS!’ Arran shouted.

Ollie grabbed a steel ball, slipped it into the pouch of his slingshot and pulled back the elastic…

There were too many of them. In his panic he wasn’t sure where to aim.

Freak was swinging his axe around wildly at the weed-covered grown-ups nearest to him. He got one in the forearm, shattering it, and on his return swing took another in the side of the head, but their numbers quickly overwhelmed him, and, as the grown-ups closed in on him, there was no longer room to use his weapon effectively. On his next strike the axe head sunk deep into a big father’s ribs and stuck there. The father twisted and writhed, churning the water, and tearing the axe from Freak’s grasp. Freak was defenceless. Wet, slimy hands closed around his neck. He struggled to throw them off, swearing at the grown-ups.

Ollie couldn’t risk a shot now – he might hit Freak, so instead he aimed at one of the grown-ups on the edge of the attacking group. A mother. He loosed a shot and struck her in the temple. She toppled over and was swallowed by the water. Then a noise made Ollie turn – more grown-ups had moved into the seating area to block their exit.

‘We’re surrounded,’ he shouted, swinging his slingshot round towards them.

Arran could do nothing to help. Grown-ups were swarming to the edge of the pool and slithering on to the tiles. He gripped his pickaxe handle and lashed out at them two-handed. A fat little father with useless legs hobbled out in a crouch, like some horrible, ungainly frog. Arran caught him under his chin with an upper-cut and he somersaulted backwards into the water.

Deke had been trying to get to his friend, but the water was thick with wallowing grown-ups. He was forcing his way onwards, using the tip of the sledgehammer’s handle as a butt. Driving it into anybody that got too close.

Achilleus was waiting on the edge. He knew that he wouldn’t be able to fight effectively in the water. He darted backwards and forwards, picking off stray grown-ups and watching Deke’s progress.

‘Go on!’ he urged him.

It looked like Deke was going to make it to Freak, but just before he got there three big grown-ups pulled Freak over and he sank beneath the surface.

‘Hold on, Freak!’

Deke powered the last few metres and dived in after his friend.

‘Idiot,’ Achilleus said again. There was nothing for it. He was going to have to go and help. He gave a war-cry and surged in, high-stepping, spear flashing in quick hard thrusts, teeth bared.

The grown-ups seemed to sense that he was dangerous and fell back. There was no sign of Freak and Deke, though.

Over by the seating area Ollie was ducked down on to one knee to steady his aim and was launching a barrage of shots towards the grown-ups blocking their way out. He couldn’t take his eyes off them for even a split second, so he had no idea what was going on behind him. He prayed that the others would join him soon, because he couldn’t keep the grown-ups at bay forever.

‘Help me, someone!’

Arran looked over and saw what was happening.

‘Achilleus,’ he shouted. ‘You get Freak and Deke. I need to help Ollie.’

He had no idea if Achilleus had heard him, and he couldn’t wait to make sure. A group of grown-ups were rushing Ollie, who couldn’t reload fast enough to hold them back. Arran raced over and ploughed in, his club flying. The wood cracked against a father’s skull. He howled and toppled sideways. Arran was finding it difficult to fight with the dog slung across his shoulders, but he swung again, this time aiming for a grown-up’s knee. There was a snap of breaking bone and the grown-up was out of action.

‘Got to push them back,’ he yelled and surged forward, driving the grown-ups over the seats and tables.

Achilleus reached the vending machine. Oblivious to the stink and the slime. He plunged a hand under the water roughly where he had last seen Deke. He grabbed hold of sodden material and tugged hard. It was a grown-up. He stuck his spear into it, twisted and pulled it out. The next moment the water boiled and erupted as Deke broke the surface, bringing Freak up with him. Freak looked confused and limp.

‘Got him,’ Deke spluttered. His face was glowing white in the gloom so that it looked almost luminous.

‘Come on,’ said Achilleus, ‘let’s go.’

But the attack wasn’t over. An enraged father bundled into them, knocking Deke hard into the vending machine and smashing the glass. Deke grunted, winded.

Achilleus dealt swiftly with the father, striking him in the mouth, and with that the remaining grown-ups gave up. They fell back as Achilleus and the other two waded towards the edge. Achilleus started taunting them, cursing and swearing and calling them all the names he could think of, daring them to attack.

‘Come on, you lazy sods! Attack me, you cowards, come on!’

But the grown-ups were melting away, slipping back under the murky surface of the pool. Achilleus felt a surge of relief; his bravado had been all show. He was exhausted, Freak and Deke had both lost their weapons, and if the grown-ups did mount a full-scale attack the boys would stand little chance. He looked back. The other two were still stumbling through the water. Deke looked like he was on his last legs. Achilleus went to him, grabbed hold of Freak round the waist and pulled the two of them along until, spluttering and slipping and stumbling, they staggered to the poolside.

‘What kept you?’ said Arran as they joined him and Ollie. The two of them had secured the seating area.

‘I had to rescue the Chuckle Brothers,’ said Achilleus.

‘We couldn’t leave without having a swim,’ said Deke, his voice hoarse and cracked. He coughed and doubled up in pain.

‘Is he all right?’ Arran asked Achilleus.

‘Think so. Come on, what’s the hold-up? Let’s get out of here.’

‘Easier said than done.’ Ollie loosed a shot at a black silhouette in the reception. ‘They’re blocking the exit.’

Achilleus swore. ‘I’ve never seen anything like this before. These are some clever bastards. They set a trap for us.’

‘These guys are getting scary,’ said Ollie.

‘We’ll get our breath back and take them,’ said Achilleus. ‘They don’t scare me.’

Deke was coughing again and shivering. He moaned. He looked whiter than ever. Freak seemed to be coming out of his daze, though. He shook his head and rubbed his temple with the heel of one hand.

‘My axe?’ he said.

‘It’s gone, Superman,’ said Achilleus. ‘Forget it. We’ll find you another one. For now we’ve just to get clear of this dump. You reckon you can walk now?’

‘I’m fine,’ said Freak.

‘Deke don’t look so hot.’

Freak turned to his friend.

‘Thanks for getting me out of that, bro,’ he said.

Deke nodded.

‘No probs.’ But his breathing was fast and shallow and there was a bubble of blood on his lips.

‘You hurt?’

Deke forced a feeble grin. ‘I think I’m poisoned.’

‘You was under the water for a long time, man, a long time,’ said Achilleus.