Percy doubted June was defenseless. At worst, this was a trap. At best, it was some kind of test.

Percy hated tests. Since he’d lost his memory, his whole life was one big fill-in-the-blank. He was ____________________, from ____________________. He felt like ____________________, and if the monsters caught him, he’d be ____________________.

Then he thought about Annabeth, the only part of his old life he was sure about. He had to find her.

“I’ll carry you.” He scooped up the old woman.

She was lighter than he expected. Percy tried to ignore her sour breath and her calloused hands clinging to his neck. He made it across the first lane of traffic. A driver honked. Another yelled something that was lost in the wind. Most just swerved and looked irritated, as if they had to deal with a lot of ratty teenagers carrying old hippie women across the freeway here in Berkeley.

A shadow fell over him. Stheno called down gleefully, “Clever boy! Found a goddess to carry, did you?”

A goddess?

June cackled with delight, muttering, “Whoops!” as a car almost killed them.

Somewhere off to his left, Euryale screamed, “Get them! Two prizes are better than one!”

Percy bolted across the remaining lanes. Somehow he made it to the median alive. He saw the gorgons swooping down, cars swerving as the monsters passed overhead. He wondered what the mortals saw through the Mist—giant pelicans? Off-course hang gliders? The wolf Lupa had told him that mortal minds could believe just about anything—except the truth.

Percy ran for the door in the hillside. June got heavier with every step. Percy’s heart pounded. His ribs ached.

One of the guards yelled. The guy with the bow nocked an arrow. Percy shouted, “Wait!”

But the boy wasn’t aiming at him. The arrow flew over Percy’s head. A gorgon wailed in pain. The second guard readied her spear, gesturing frantically at Percy to hurry.

Fifty feet from the door. Thirty feet.

“Gotcha!” shrieked Euryale. Percy turned as an arrow thudded into her forehead. Euryale tumbled into the fast lane. A truck slammed into her and carried her backward a hundred yards, but she just climbed over the cab, pulled the arrow out of her head, and launched back into the air.

Percy reached the door. “Thanks,” he told the guards. “Good shot.”

“That should’ve killed her!” the archer protested.

“Welcome to my world,” Percy muttered.

“Frank,” the girl said. “Get them inside, quick! Those are gorgons.”

“Gorgons?” The archer’s voice squeaked. It was hard to tell much about him under the helmet, but he looked stout like a wrestler, maybe fourteen or fifteen. “Will the door hold them?”

In Percy’s arms, June cackled. “No, no it won’t. Onward, Percy Jackson! Through the tunnel, over the river!”

“Percy Jackson?” The female guard was darker-skinned, with curly hair sticking out the sides of her helmet. She looked younger than Frank—maybe thirteen. Her sword scabbard came down almost to her ankle. Still, she sounded like she was the one in charge. “Okay, you’re obviously a demigod. But who’s the—?” She glanced at June. “Never mind. Just get inside. I’ll hold them off.”

“Hazel,” the boy said. “Don’t be crazy.”

“Go!” she demanded.

Frank cursed in another language—was that Latin?—and opened the door. “Come on!”

Percy followed, staggering under the weight of the old lady, who was definitely getting heavier. He didn’t know how that girl Hazel would hold off the gorgons by herself, but he was too tired to argue.

The tunnel cut through solid rock, about the width and height of a school hallway. At first, it looked like a typical maintenance tunnel, with electric cables, warning signs, and fuse boxes on the walls, lightbulbs in wire cages along the ceiling. As they ran deeper into the hillside, the cement floor changed to tiled mosaic. The lights changed to reed torches, which burned but didn’t smoke. A few hundred yards ahead, Percy saw a square of daylight.

The old lady was heavier now than a pile of sandbags. Percy’s arms shook from the strain. June mumbled a song in Latin, like a lullaby, which didn’t help Percy concentrate.

Behind them, the gorgons’ voices echoed in the tunnel. Hazel shouted. Percy was tempted to dump June and runback to help, but then the entire tunnel shook with the rumble of falling stone. There was a squawking sound, just like the gorgons had made when Percy had dropped a crate of bowling balls on them in Napa. He glanced back. The west end of the tunnel was now filled with dust.

“Shouldn’t we check on Hazel?” he asked.

“She’ll be okay—I hope,” Frank said. “She’s good underground. Just keep moving! We’re almost there.”

“Almost where?”

June chuckled. “All roads lead there, child. You should know that.”

“Detention?” Percy asked.

“Rome, child,” the old woman said. “Rome.”

Percy wasn’t sure he’d heard her right. True, his memory was gone. His brain hadn’t felt right since he had woken up at the Wolf House. But he was pretty sure Rome wasn’t in California.

They kept running. The glow at the end of the tunnel grew brighter, and finally they burst into sunlight.

Percy froze. Spread out at his feet was a bowl-shaped valley several miles wide. The basin floor was rumpled with smaller hills, golden plains, and stretches of forest. A small clear rivercut a winding course from a lake in the center and around the perimeter, like a capital G.

The geography could’ve been anywhere in northern California—live oaks and eucalyptus trees, gold hills and blue skies. That big inland mountain—what was it called, Mount Diablo?—rose in the distance, right where it should be.

But Percy felt like he’d stepped into a secret world. In the center of the valley, nestled by the lake, was a small city of white marble buildings with red-tiled roofs. Some had domes and columned porticoes, like national monuments. Others looked like palaces, with golden doors and large gardens. He could see an open plaza with freestanding columns, fountains, and statues. A five-story-tall Roman coliseum gleamed in the sun, next to a long oval arena like a racetrack.

Across the lake to the south, another hill was dotted with even more impressive buildings—temples, Percy guessed. Several stone bridges crossed the river as it wound through the valley, and in the north, a long line of brickwork arches stretched from the hills into the town. Percy thought it looked like an elevated train track. Then he realized it must be an aqueduct.

The strangest part of the valley was right below him. About two hundred yards away, just across the river, was some sort of military encampment. It was about a quarter mile square, with earthen ramparts on all four sides, the tops lined with sharpened spikes. Outside the walls ran a dry moat, also studded with spikes. Wooden watchtowers rose at each corner, manned by sentries with oversized, mounted crossbows. Purple banners hung from the towers. A wide gateway opened on the far side of camp, leading toward the city. A narrower gate stood closed on the riverbank side. Inside, the fortress bustled with activity: dozens of kids going to and from barracks, carrying weapons, polishing armor. Percy heard the clank of hammers at a forge and smelled meat cooking over a fire.

Something about this place felt very familiar, yet not quite right.

“Camp Jupiter,” Frank said. “We’ll be safe once—”

Footsteps echoed in the tunnel behind them. Hazel burst into the light. She was covered with stone dust and breathing hard. She’d lost her helmet, so her curly brown hair fell around her shoulders. Her armor had long slash marks in front from the claws of a gorgon. One of the monsters had tagged her with a 50% off sticker.

“I slowed them down,” she said. “But they’ll be here any second.”

Frank cursed. “We have to get across the river.”

June squeezed Percy’s neck tighter. “Oh, yes, please. I can’t get my dress wet.”

Percy bit his tongue. If this lady was a goddess, she must’ve been the goddess of smelly, heavy, useless hippies. But he’d come this far. He’d better keep lugging her along.

It’s a kindness, she’d said. And if you don’t, the gods will die, the world we know will perish, and everyone from your old life will be destroyed.

If this was a test, he couldn’t afford to get an F.

He stumbled a few times as they ran for the river. Frank and Hazel kept him on his feet.

They reached the riverbank, and Percy stopped to catch his breath. The current was fast, but the river didn’t look deep. Only a stone’s throw across stood the gates of the fort.

“Go, Hazel.” Frank nocked two arrows at once. “Escort Percy so the sentries don’t shoot him. It’s my turn to hold off the baddies.”

Hazel nodded and waded into the stream.

Percy started to follow, but something made him hesitate. Usually he loved the water, but this river seemed…powerful, and not necessarily friendly.

“The Little Tiber,” said June sympathetically. “It flows with the power of the original Tiber, river of the empire. This is your last chance to back out, child. The mark of Achilles is a Greek blessing. You can’t retain it if you cross into Roman territory. The Tiber will wash it away.”

Percy was too exhausted to understand all that, but he got the main point. “If I cross, I won’t have iron skin anymore?”

June smiled. “So what will it be? Safety, or a future of pain and possibility?”

Behind him, the gorgons screeched as they flew from the tunnel. Frank let his arrows fly.

From the middle of the river, Hazel yelled, “Percy, come on!”

Up on the watchtowers, horns blew. The sentries shouted and swiveled their crossbows toward the gorgons.

Annabeth, Percy thought. He forged into the river. It was icy cold, much swifter than he’d imagined, but that didn’t bother him. New strength surged through his limbs. His senses tingled like he’d been injected with caffeine. He reached the other side and put the old woman down as the camp’s gates opened. Dozens of kids in armor poured out.

Hazel turned with a relieved smile. Then she looked over Percy’s shoulder, and her expression changed to horror. “Frank!”

Frank was halfway across the river when the gorgons caught him. They swooped out of the sky and grabbed him by either arm. He screamed in pain as their claws dug into his skin.

The sentries yelled, but Percy knew they couldn’t get a clear shot. They’d end up killing Frank. The other kids drew swords and got ready to charge into the water, but they’d be too late.

There was only one way.

Percy thrust out his hands. An intense tugging sensation filled his gut, and the Tiber obeyed his will. The river surged. Whirlpools formed on either side of Frank. Giant watery hands erupted from the stream, copying Percy’s movements. The giant hands grabbed the gorgons, who dropped Frank in surprise. Then the hands lifted the squawking monsters in a liquid vise grip.

Percy heard the other kids yelping and backing away, but he stayed focused on his task. He made a smashing gesture with his fists, and the giant hands plunged the gorgons into the Tiber. The monsters hit bottom and broke into dust. Glittering clouds of gorgon essence struggled to re-form, but the river pulled them apart like a blender. Soon every trace of the gorgons was swept downstream. The whirlpools vanished, and the current returned to normal.