'Castor! Castor! Wake up!'

'I can't feel a pulse, I think we're losing him.'

'Oh gods, Castor, open your eyes!'

'There isn't much time. We need to leave.'

'Not without him!'

'Alyx, come on –'

I coughed and spluttered, finally managing to wrest my eyes open. Around me crouched my friends from Camp Half-Blood, along with a bunch of kids in purple t-shirts carrying short swords and rectangular shields. They looked like they meant business.

I almost passed out again as Alyx enveloped me in a spine-crushing hug.

'You're OK!' she said, her voice muffled as she buried her head in my shoulder. 'I thought for a second…'

Alyx trailed off.

I looked around me. The bus was flipped on its side, with the front engine ablaze. Someone had pulled me out and lay me on the grass bank. Passengers were staggering out of the wreckage, looking dazed and bruised but otherwise unhurt.

'What the hell happened? I asked incredulously.

'We engaged the target using lethal force' answered one of the kids in purple. He was a short guy, but heavily built, and looked about fifteen. He had a savage buzzcut and an expression that told me he took himself way too seriously. 'My unit spotted a high value military target, and we responded appropriately with minimum casualties.'

Ross rolled his eyes.

'Jeez, who let Ranger Rick out of the box?' he asked.

The guy bristled.

'My name is Centurion Jack Davis, of the fourth legion' he told Ross, self-importantly.

'Acting Centurion' cut in another purple shirt. 'You're only in charge because Melvin's got food poisoning.'

This guy reminded me of Leo back at Camp Half-Blood. He had curly black hair and a mischievous glint in his eyes.

Jack puffed his chest.

'Don't backchat me in front of the Greeks, Diego, or I'll put you on latrine duty.'

'You can't do that, only permanent Centurions can.'

'Then I'll… uh… write a scathing letter about you to the praetor.'

'Go on then' Diego grinned.

'GUYS!' Annabeth yelled. 'Shut up! We're grateful for your help, but we really need to leave.'

'What's the rush?' Percy asked.

Annabeth wordlessly pointed towards the wreckage of the bus, which had begun to tremble and shift.

There came a screeching as metal buckled. The roof of the bus tore open, revealing two scorched but very much still operating automatons. And they did not look happy.

'Ah' said Percy. 'I see. Castor, can you walk? Or better yet, run?'

Jack motioned to one of his purple shirted friends.

'I can buy us some time. Everyone cover their ears.'

From a large wheelie-bag Jack produced what looked like a long metal tube with a scope and trigger attached.

My eyes bulged.

'Uhhhh, dude is that a…'

'Military grade surface-to-air missile launcher?' Jack asked offhandedly. 'Yup. Well, with a few of my own modifications.'

'Jack!' Diego groaned. 'Reyna told you to stop bringing missile launchers on missions. Where do you even get them?'

Jack ignored him.

'Everyone get down!' he called.

Brad and Chad, the automatons, had started running towards us, their limbs whirring. Jack put the launcher to his shoulder, aimed, then fired.

The explosion knocked me off my feet and sent me rolling along the grass. I lay on my back, panting.

'Alright, let's move out!' Jack was yelling. 'Ten-four, look alive!'

His comrade, Diego, pulled a long-suffering look before organising the rest of the campers into a line that started running.

'Castor, we've gotta go!' It was Percy, standing over me, and holding out his hand. I took it, and Percy hauled me to my feet.

'Who are these people?' I asked Percy, leaning on him for support.

'They're Roman demi-gods' he told me. 'From Camp Jupiter. Not a bad bunch, but a little… intense, at times.'

I looked around, and saw a sign next to the road that showed we were in the Bay Area. A few days ago, I would have thought that impossible. Now, a vehicle bending space and time didn't even warrant an eyebrow raise.

'How are we getting to Camp Jupiter?' Annabeth asked Jack.

'There's an Aeneas passage close by' Diego said. 'It's where we were stationed when you guys came up on the radar.'

He gave us all a sideway glance.

'What happened anyway? We haven't heard from Camp-Half Blood in months. Then suddenly you guys turn up in a bus going a thousand miles per second and scrapping with automatons.'

'We'll explain it all when we get to Camp' Annabeth said. 'But we need to talk to Frank and Reyna. Urgently.'

'Frank's not here' Diego told us. 'Him and Hazel went on a romantic weekend getaway. That was a month ago. Reyna's been tearing her hair out trying to find them, but it's like they've disappeared into thin air.'

'I hope they're OK' Percy muttered.

Annabeth threw him a tired grin.

'They're both tough as nails. I'm sure they're fine. But I wonder if their disappearance is linked…'

'Company, halt!' Jack shouted. The Romans ground to stop.

I looked around.

'Where's this passage?'

Diego pointed at a manhole, leading down to the sewer beneath the highway.

'Through there.'

Ross made a face.

'C'mon, really? Why'd you have to put through there?'

'We don't control where the passages spring up' Jack replied, testily. 'They're along divine lines of power, that's just how it works. Now – '

In the distance, came a clanking and whirring sound.

Percy swore.

'No time for arguing. Ross, you go first.'

Ross grumbled as he opened the manhole cover and lowered himself in.