Jason tried to take advantage. He stepped inside the giant’s guard and stabbed at his chest, but somehow Ephialtes parried the strike. He sliced the tip of his spear down Jason’s chest, ripping his purple shirt into a vest. Jason stumbled, looking at the thin line of blood down his sternum. Ephialtes kicked him backward.

Up in the emperor’s box, Piper cried out, but her voice was drowned in the roar of the crowd. Bacchus looked on with an amused smile, munching from a bag of Doritos.

Ephialtes towered over Percy and Jason, both halves of his broken spear poised over their heads. Percy’s sword arm was numb. Jason’s gladius had skittered across the arena floor. Their plan had failed.

Percy glanced up at Bacchus, deciding what final curse he would hurl at the useless wine god, when he saw a shape in the sky above the Colosseum—a large dark oval descending rapidly.

From the lake, Otis yelled, trying to warn his brother, but his half-dissolved face could only manage: “Uh-umh-moooo!”

“Don’t worry, brother!” Ephialtes said, his eyes still fixed on the demigods. “I will make them suffer!”

The Argo II turned in the sky, presenting its port side, and green fire blazed from the ballista.

“Actually,” Percy said. “Look behind you.”

He and Jason rolled away as Ephialtes turned and bellowed in disbelief.

Percy dropped into a trench just as the explosion rocked the Colosseum.

When he climbed out again, the Argo II was coming in for a landing. Jason poked his head out from behind his improvised bomb shelter of a plastic horse. Ephialtes lay charred and groaning on the arena floor, the sand around him seared into a halo of glass by the heat of the Greek fire. Otis was floundering in the lake, trying to re-form, but from the arms down he looked like a puddle of burnt oatmeal.

Percy staggered over to Jason and clapped him on the shoulder. The ghostly crowd gave them a standing ovation as the Argo II extended its landing gear and settled on the arena floor. Leo stood at the helm, Hazel and Frank grinning at his side. Coach Hedge danced around the firing platform, pumping his fist in the air and yelling, “That’s what I’m talking about!”

Percy turned to the emperor’s box. “Well?” he yelled at Bacchus. “Was that entertaining enough for you, you wine-breathed little—”

“No need for that.” Suddenly the god was standing right next to him in the arena. He brushed Dorito dust off his purple robes. “I have decided you are worthy partners for this combat.”

“Partners?” Jason growled. “You did nothing!”

Bacchus walked to the edge of the lake. The water instantly drained, leaving an Otis-headed pile of mush. Bacchus picked his way to the bottom and looked up at the crowd. He raised his thyrsus.

The crowd jeered and hollered and pointed their thumbs down. Percy had never been sure whether that meant live or die. He’d heard it both ways.

Bacchus chose the more entertaining option. He smacked Otis’s head with his pinecone staff, and the giant pile of Otismeal disintegrated completely.

The crowd went wild. Bacchus climbed out of the lake and strutted over to Ephialtes, who was still lying spread-eagled, overcooked and smoking.

Again, Bacchus raised his thyrsus.

“DO IT!” the crowd roared.

“DON’T DO IT!” Ephialtes wailed.

Bacchus tapped the giant on the nose, and Ephialtes crumbled to ashes.

The ghosts cheered and threw spectral confetti as Bacchus strode around the stadium with his arms raised triumphantly, exulting in the worship. He grinned at the demigods. “That, my friends, is a show! And of course I did something. I killed two giants!”

As Percy’s friends disembarked from the ship, the crowd of ghosts shimmered and disappeared. Piper and Nico struggled down from the emperor’s box as the Colosseum’s magical renovations began to turn into mist. The arena floor remained solid, but otherwise the stadium looked as if it hadn’t hosted a good giant killing for eons.

“Well,” Bacchus said. “That was fun. You have my permission to continue your voyage.”

“Your permission?” Percy snarled.

“Yes.” Bacchus raised an eyebrow. “Although your voyage may be a little harder than you expect, son of Neptune.”

“Poseidon,” Percy corrected him automatically. “What do you mean about my voyage?”

“You might try the parking lot behind the Emmanuel Building,” Bacchus said. “Best place to break through. Now, good-bye, my friends. And, ah, good luck with that other little matter.”

The god vaporized in a cloud of mist that smelled faintly of grape juice. Jason ran to meet Piper and Nico.

Coach Hedge trotted up to Percy, with Hazel, Frank, and Leo close behind. “Was that Dionysus?” Hedge asked. “I love that guy!”

“You’re alive!” Percy said to the others. “The giants said you were captured. What happened?”

Leo shrugged. “Oh, just another brilliant plan by Leo Valdez. You’d be amazed what you can do with an Archimedes sphere, a girl who can sense stuff underground, and a weasel.”

“I was the weasel,” Frank said glumly.

“Basically,” Leo explained, “I activated a hydraulic screw with the Archimedes device—which is going to be awesome once I install it in the ship, by the way. Hazel sensed the easiest path to drill to the surface. We made a tunnel big enough for a weasel, and Frank climbed up with a simple transmitter that I slapped together. After that, it was just a matter of hacking into Coach Hedge’s favorite satellite channels and telling him to bring the ship around to rescue us. After he got us, finding you was easy, thanks to that godly light show at the Colosseum.”

Percy understood about ten percent of Leo’s story, but he decided it was enough since he had a more pressing question. “Where’s Annabeth?”

Leo winced. “Yeah, about that…she’s still in trouble, we think. Hurt, broken leg, maybe—at least according to this vision Gaea shown us. Rescuing her is our next stop.”

Two seconds before, Percy had been ready to collapse. Now another surge of adrenaline coursed through his body. He wanted to strangle Leo and demand why the Argo II hadn’t sailed off to rescue Annabeth first, but he thought that might sound a little ungrateful.

“Tell me about the vision,” he said. “Tell me everything.”

The floor shook. The wooden planks began to disappear, spilling sand into the pits of the hypogeum below.

“Let’s talk on board,” Hazel suggested. “We’d better take off while we still can.”

They sailed out of the Colosseum and veered south over the rooftops of Rome.

All around the Piazza del Colosseo, traffic had come to a standstill. A crowd of mortals had gathered, probably wondering about the strange lights and sounds that had come from the ruins. As far as Percy could see, none of the giants’ spectacular plans for destruction had come off successfully. The city looked the same as before. No one seemed to notice the huge Greek trireme rising into the sky.

The demigods gathered around the helm. Jason bandaged Piper’s sprained shoulder while Hazel sat at the stern, feeding Nico ambrosia. The son of Hades could barely lift his head. His voice was so quiet, Hazel had to lean in whenever he spoke.

Frank and Leo recounted what had happened in the room with the Archimedes spheres, and the visions Gaea had shown them in the bronze mirror. They quickly decided that their best lead for finding Annabeth was the cryptic advice Bacchus had provided: the Emmanuel Building, whatever that was. Frank started typing at the helm’s computer while Leo tapped furiously at his controls, muttering, “Emmanuel Building. Emmanuel Building.” Coach Hedge tried to help by wrestling with an upside-down street map of Rome.

Percy knelt next to Jason and Piper. “How’s the shoulder?”

Piper smiled. “It’ll heal. Both of you did great.”

Jason elbowed Percy. “Not a bad team, you and me.”

“Better than jousting in a Kansas cornfield,” Percy agreed.

“There it is!” Leo cried, pointing to his monitor. “Frank, you’re amazing! I’m setting course.”

Frank hunched his shoulders. “I just read the name off the screen. Some Chinese tourist marked it on Google Maps.”

Leo grinned at the others. “He reads Chinese.”

“Just a tiny bit,” Frank said.

“How cool is that?”

“Guys,” Hazel broke in. “I hate to interrupt your admiration session, but you should hear this.”

She helped Nico to his feet. He’d always been pale, but now his skin looked like powdered milk. His dark sunken eyes reminded Percy of photos he’d seen of liberated prisoners-of-war, which Percy guessed Nico basically was.

“Thank you,” Nico rasped. His eyes darted nervously around the group. “I’d given up hope.”

The past week or so, Percy had imagined a lot of scathing things he might say to Nico when they met again, but the guy looked so frail and sad, Percy couldn’t muster much anger.

“You knew about the two camps all along,” Percy said. “You could have told me who I was the first day I arrived at Camp Jupiter, but you didn’t.”

Nico slumped against the helm. “Percy, I’m sorry. I discovered Camp Jupiter last year. My dad led me there, though I wasn’t sure why. He told me the gods had kept the camps separate for centuries and that I couldn’t tell anyone. The time wasn’t right. But he said it would be important for me to know…” He doubled over in a fit of coughing.

Hazel held his shoulders until he could stand again.

“I—I thought Dad meant because of Hazel,” Nico continued. “I’d need a safe place to take her. But now…I think he wanted me to know about both camps so I’d understand how important your quest was, and so I’d search for the Doors of Death.”

The air turned electric—literally, as Jason started throwing off sparks.

“Did you find the doors?” Percy asked.

Nico nodded. “I was a fool. I thought I could go anywhere in the Underworld, but I walked right into Gaea’s trap. I might as well have tried running from a black hole.”

“Um…” Frank chewed his lip. “What kind of black hole are you talking about?”

Nico started to speak, but whatever he needed to say must have been too terrifying. He turned to Hazel.

She put her hand on her brother’s arm. “Nico told me that the Doors of Death have two sides—one in the mortal world, one in the Underworld. The mortal side of the portal is in Greece. It’s heavily guarded by Gaea’s forces. That’s where they brought Nico back into the upper world. Then they transported him to Rome.”

Piper must’ve been nervous, because her cornucopia spit out a cheeseburger. “Where exactly in Greece is this doorway?”

Nico took a rattling breath. “The House of Hades. It’s an underground temple in Epirus. I can mark it on a map, but—but the mortal side of the portal isn’t the problem. In the Underworld, the Doors of Death are in…in…”