Leo frantically worked the ship's controls. 'Oars won't retract. Get it away! Get it away!'

Up in the rigging, Nico's face was slack with shock.

'Styx it's huge!' he yelled. 'Port! Go port!'

Coach Hedge was the last one on deck. He compensated for that with enthusiasm. He bounded up the steps, waving his baseball bat, and without hesitation goat-galloped to the stern and leaped over the rail with a gleeful 'Ha-HA!'

Hazel staggered towards the quarterdeck to join her friends. The boat shuddered. More oars snapped, and Leo yelled, 'No, no, no! Dang slimy-sh.e.l.led son of a mother!'

Hazel reached the stern and couldn't believe what she saw.

When she heard the word turtle, she thought of a cute little thing the size of a jewellery box, sitting on a rock in the middle of a fishpond. When she heard huge, her mind tried to adjust okay, perhaps it was like the Galapagos tortoise she'd seen in the zoo once, with a sh.e.l.l big enough to ride on.

She did not envision a creature the size of an island. When she saw the ma.s.sive dome of craggy black and brown squares, the word turtle simply did not compute. Its sh.e.l.l was more like a landma.s.s hills of bone, shiny pearl valleys, kelp and moss forests, rivers of seawater trickling down the grooves of its carapace.

On the ship's starboard side, another part of the monster rose from the water like a submarine.

Lares of Rome ... was that its head?

Its gold eyes were the size of wading pools, with dark sideways slits for pupils. Its skin glistened like wet army camouflage brown flecked with green and yellow. Its red, toothless mouth could've swallowed the Athena Parthenos in one bite.

Hazel watched as it snapped off half a dozen oars.

'Stop that!' Leo wailed.

Coach Hedge clambered around the turtle's sh.e.l.l, whacking at it uselessly with his baseball bat and yelling, 'Take that! And that!'

Jason flew from the stern and landed on the creature's head. He stabbed his golden sword straight between its eyes, but the blade slipped sideways, as if the turtle's skin were greased steel. Frank shot arrows at the monster's eyes with no success. The turtle's filmy inner eyelids blinked with uncanny precision, deflecting each shot. Piper shot cantaloupes into the water, yelling, 'Fetch, ya stupid turtle!' But the turtle seemed fixated on eating the Argo II.

'How did it get so close?' Hazel demanded.

Leo threw his hands up in exasperation. 'Must be that sh.e.l.l. Guess it's invisible to sonar. It's a freaking stealth turtle!'

'Can the ship fly?' Piper asked.

'With half our oars broken off?' Leo punched some b.u.t.tons and spun his Archimedes sphere. 'I'll have to try something else.'

'There!' Nico yelled from above. 'Can you get us to those straits?'

Hazel looked where he was pointing. About half a mile to the east, a long strip of land ran parallel to the coastal cliffs. It was hard to be sure from a distance, but the stretch of water between them looked to be only twenty or thirty yards across possibly wide enough for the Argo II to slip through, but definitely not wide enough for the giant turtle's sh.e.l.l.

'Yeah. Yeah.' Leo apparently understood. He turned the Archimedes sphere. 'Jason, get away from that thing's head! I have an idea!'

Jason was still hacking away at the turtle's face, but when he heard Leo say, 'I have an idea,' he made the only smart choice. He flew away as fast as possible.

'Coach, come on!' Jason said.

'No, I got this!' Hedge said, but Jason grabbed him around the waist and took off. Unfortunately, the coach struggled so much that Jason's sword fell out of his hand and splashed into the sea.

'Coach!' Jason complained.

'What?' Hedge said. 'I was softening him up!'

The turtle head-b.u.t.ted the hull, almost tossing the whole crew off the port side. Hazel heard a cracking sound, like the keel had splintered.

'Just another minute,' Leo said, his hands flying over the console.

'We might not be here in another minute!' Frank fired his last arrow.

Piper yelled at the turtle, 'Go away!'

For a moment, it actually worked. The turtle turned from the ship and dipped its head underwater. But then it came right back and rammed them even harder.

Jason and Coach Hedge landed on the deck.

'You all right?' Piper asked.

'Fine,' Jason muttered. 'Without a weapon, but fine.'

'Fire in the sh.e.l.l!' Leo cried, spinning his Wii controller.

Hazel thought the stern had exploded. Jets of fire blasted out behind them, washing over the turtle's head. The ship shot forward and threw Hazel to the deck again.

She hauled herself up and saw that the ship was bouncing over the waves at incredible speed, trailing fire like a rocket. The turtle was already a hundred yards behind them, its head charred and smoking.

The monster bellowed in frustration and started after them, its paddle feet scooping through the water with such power that it actually started to gain on them. The entrance to the straits was still a quarter mile ahead.

'A distraction,' Leo muttered. 'We'll never make it unless we get a distraction.'

'A distraction,' Hazel repeated.

She concentrated and thought: Arion!

She had no idea whether it would work. But instantly Hazel spotted something on the horizon a flash of light and steam. It streaked across the surface of the Adriatic. In a heartbeat, Arion stood on the quarterdeck.

G.o.ds of Olympus, Hazel thought. I love this horse.

Arion snorted as if to say, Of course you do. You're not stupid.

Hazel climbed on his back. 'Piper, I could use that charmspeak of yours.'

'Once upon a time, I liked turtles,' Piper muttered, accepting a hand up. 'Not any more!'

Hazel spurred Arion. He leaped over the side of the boat, hitting the water at a full gallop.

The turtle was a fast swimmer, but it couldn't match Arion's speed. Hazel and Piper zipped around the monster's head, Hazel slicing with her sword, Piper shouting random commands like, 'Dive! Turn left! Look behind you!'

The sword did no damage. Each command only worked for a moment, but they were making the turtle very annoyed. Arion whinnied derisively as the turtle snapped at him, only to get a mouthful of horse vapour.

Soon the monster had completely forgotten the Argo II. Hazel kept stabbing at its head. Piper kept yelling commands and using her cornucopia to bounce coconuts and roasted chickens off the turtle's eyeb.a.l.l.s.

As soon as the Argo II had pa.s.sed into the straits, Arion broke off his hara.s.sment. They sped after the ship, and a moment later were back on deck.

The rocket fire had extinguished, though smoking bronze exhaust vents still jutted from the stern. The Argo II limped forward under sail power, but their plan had paid off. They were safely harboured in the narrow waters, with a long, rocky island to starboard and the sheer white cliffs of the mainland to port. The turtle stopped at the entrance to the straits and glared at them balefully, but it made no attempt to follow. Its sh.e.l.l was obviously much too wide.

Hazel dismounted and got a big hug from Frank. 'Nice work out there!' he said.

Her face flushed. 'Thanks.'

Piper slid down next to her. 'Leo, since when do we have jet propulsion?'

'Aw, you know ...' Leo tried to look modest and failed. 'Just a little something I whipped up in my spare time. Wish I could've given you more than a few seconds of burn, but at least it got us out of there.'

'And roasted the turtle's head,' Jason said appreciatively. 'So what now?'

'Kill it!' Coach said. 'You even have to ask? We got enough distance. We got ballistae. Lock and load, demiG.o.ds!'

Jason frowned. 'Coach, first of all, you made me lose my sword.'

'Hey! I didn't ask for an evac!'

'Second, I don't think the ballistae will do any good. That sh.e.l.l is like Nemean Lion skin. Its head isn't any softer.'

'So we chuck one right down its throat,' Coach said, 'like you guys did with that shrimp monster thing in the Atlantic. Light it up from the inside.'

Frank scratched his head. 'Might work. But then you've got a five-million-kilo turtle carca.s.s blocking the entrance to the straits. If we can't fly with the oars broken, how do we get the ship out?'

'You wait and fix the oars!' Coach said. 'Or just sail in the other direction, you big galoot.'

Frank looked confused. 'What's a galoot?'

'Guys!' Nico called down from the mast. 'About sailing in the other direction? I don't think that's going to work.'

He pointed past the prow.

A quarter mile ahead of them, the long rocky strip of land curved in and met the cliffs. The channel ended in a narrow V.

'We're not in a strait,' Jason said. 'We're in a dead end.'

Hazel got a cold feeling in her fingers and toes. On the port rail, Gale the weasel sat up on her haunches, staring at Hazel expectantly.

'This is a trap,' Hazel said.

The others looked at her.

'Nah, it's fine,' Leo said. 'Worst that happens, we make repairs. Might take overnight, but I can get the ship flying again.'

At the mouth of the inlet, the turtle roared. It didn't appear interested in leaving.

'Well ...' Piper shrugged. 'At least the turtle can't get us. We're safe here.'

That was something no demiG.o.d should ever say. The words had barely left Piper's mouth when an arrow sank into the mainmast, six inches from her face.

The crew scattered for cover, except for Piper, who stood frozen in place, gaping at the arrow that had almost pierced her nose the hard way.

'Piper, duck!' Jason whispered harshly.

But no other missiles rained down.

Frank studied the angle of the bolt in the mast and pointed towards the top of the cliffs.

'Up there,' he said. 'Single shooter. See him?'

The sun was in her eyes, but Hazel spotted a tiny figure standing at the top of the ledge. His bronze armour glinted.

'Who the heck is he?' Leo demanded. 'Why is he firing at us?'

'Guys?' Piper's voice was thin and watery. 'There's a note.'

Hazel hadn't seen it before, but a parchment scroll was tied to the arrow shaft. She wasn't sure why, but that made her angry. She stormed over and untied it.

'Uh, Hazel?' Leo said. 'You sure that's safe?'

She read the note out loud. 'First line: Stand and deliver.'

'What does that mean?' Coach Hedge complained. 'We are standing. Well, crouching, anyway. And if that guy is expecting a pizza delivery, forget it!'

'There's more,' Hazel said. 'This is a robbery. Send two of your party to the top of the cliff with all your valuables. No more than two. Leave the magic horse. No flying. No tricks. Just climb.'

'Climb what?' Piper asked.

Nico pointed. 'There.'

A narrow set of steps was carved into the cliff, leading to the top. The turtle, the dead-end channel, the cliff ... Hazel got the feeling this was not the first time the letter writer had ambushed a ship here.

She cleared her throat and kept reading aloud: 'I do mean all your valuables. Otherwise my turtle and I will destroy you. You have five minutes.'

'Use the catapults!' cried the coach.

'P.S.' Hazel read, 'don't even think about using your catapults.'

'Curse it!' said the coach. 'This guy is good.'

'Is the note signed?' Nico asked.

Hazel shook her head. She'd heard a story back at Camp Jupiter, something about a robber who worked with a giant turtle, but, as usual, as soon as she needed the information it sat annoyingly in the back of her memory, just out of reach.

The weasel Gale watched her, waiting to see what she would do.