The Doors were still too far away to make out much detail, but the Titans flanking either side were familiar enough. The one on the left wore shining golden armor that shimmered with heat.

“Hyperion,” Percy muttered. “That guy just won’t stay dead.”

The one on the right wore dark-blue armor, with ram’s horns curling from the sides of his helmet. Percy had only seen him in dreams before, but it was definitely Krios, the Titan that Jason had killed in the battle for Mount Tam.

“Bob’s other brothers,” Annabeth said. The Death Mist shimmered around her, temporarily turning her face into a grinning skull. “Bob, if you have to fight them, can you?”

Bob hefted his broom, like he was ready for a messy cleaning job. “We must hurry,” he said, which Percy noticed wasn’t really an answer. “Follow me.”

SO FAR, THEIR DEATH MIST camouflage plan seemed to be working. So, naturally, Percy expected a massive last-minute fail.

Fifty feet from the Doors of Death, he and Annabeth froze.

“Oh, gods,” Annabeth murmured. “They’re the same.”

Percy knew what she meant. Framed in Stygian iron, the magical portal was a set of elevator doors—two panels of silver and black etched with art deco designs. Except for the fact that the colors were inverted, they looked exactly like the elevators in the Empire State Building, the entrance to Olympus.

Seeing them, Percy felt so homesick, he couldn’t breathe. He didn’t just miss Mount Olympus. He missed everything he’d left behind: New York City, Camp Half-Blood, his mom and stepdad. His eyes stung. He didn’t trust himself to talk.

The Doors of Death seemed like a personal insult, designed to remind him of everything he couldn’t have.

As he got over his initial shock, he noticed other details: the frost spreading from the base of the Doors, the purplish glow in the air around them, and the chains that held them fast.

Cords of black iron ran down either side of the frame, like rigging lines on a suspension bridge. They were tethered to hooks embedded in the fleshy ground. The two Titans, Krios and Hyperion, stood guard at the anchor points.

As Percy watched, the entire frame shuddered. Black lightning flashed into the sky. The chains shook, and the Titans planted their feet on the hooks to keep them secure. The Doors slid open, revealing the gilded interior of an elevator car.

Percy tensed, ready to charge forward, but Bob planted a hand on his shoulder. “Wait,” he cautioned.

Hyperion yelled to the surrounding crowd: “Group A-22! Hurry up, you sluggards!”

A dozen Cyclopes rushed forward, waving little red tickets and shouting excitedly. They shouldn’t have been able to fit inside those human-sized doors, but as the Cyclopes got close, their bodies distorted and shrank, the Doors of Death sucking them inside.

The Titan Krios jabbed his thumb against the up button on the elevator’s right side. The Doors slid closed.

The frame shuddered again. Dark lightning faded.

“You must understand how it works,” Bob muttered. He addressed the kitten in his palm, maybe so the other monsters wouldn’t wonder who he was talking to. “Each time the Doors open, they try to teleport to a new location. Thanatos made them this way, so only he could find them. But now they are chained. The Doors cannot relocate.”

“Then we cut the chains,” Annabeth whispered.

Percy looked at the blazing form of Hyperion. The last time he’d fought the Titan, it had taken every ounce of his strength. Even then Percy had almost died. Now there were two Titans, with several thousand monsters for backup.

“Our camouflage,” he said. “Will it disappear if we do something aggressive, like cutting the chains?”

“I do not know,” Bob told his kitten.

“Mrow,” said Small Bob.

“Bob, you’ll have to distract them,” Annabeth said. “Percy and I will sneak around the two Titans and cut the chains from behind.”

“Yes, fine,” Bob said. “But that is only one problem. Once you are inside the Doors, someone must stay outside to push the button and defend it.”

Percy tried to swallow. “Uh…defend the button?”

Bob nodded, scratching his kitten under the chin. “Someone must keep pressing the UP button for twelve minutes, or the journey will not finish.”

Percy glanced at the Doors. Sure enough, Krios still had his thumb jammed on the UP button. Twelve minutes… Somehow, they would have to get the Titans away from those doors. Then Bob, Percy, or Annabeth would have to keep that button pushed for twelve long minutes, in the middle of an army of monsters in the heart of Tartarus, while the other two rode to the mortal world. It was impossible.

“Why twelve minutes?” Percy asked.

“I do not know,” Bob said. “Why twelve Olympians, or twelve Titans?”

“Fair enough,” Percy said, though he had a bitter taste in his mouth.

“What do you mean the journey won’t finish?” Annabeth asked. “What happens to the passengers?”

Bob didn’t answer. Judging from his pained expression, Percy decided he didn’t want to be in that elevator if the car stalled between Tartarus and the mortal world.

“If we do push the button for twelve minutes,” Percy said, “and the chains are cut—”

“The Doors should reset,” Bob said. “That is what they are supposed to do. They will disappear from Tartarus. They will appear somewhere else, where Gaea cannot use them.”

“Thanatos can reclaim them,” Annabeth said. “Death goes back to normal, and the monsters lose their shortcut to the mortal world.”

Percy exhaled. “Easy-peasy. Except for…well, everything.”

Small Bob purred.

“I will push the button,” Bob volunteered.

A mix of feelings churned in Percy’s gut—grief, sadness, gratitude, and guilt thickening into emotional cement. “Bob, we can’t ask you to do that. You want to go through the Doors too. You want to see the sky again, and the stars, and—”

“I would like that,” Bob agreed. “But someone must push the button. And once the chains are cut…my brethren will fight to stop your passage. They will not want the Doors to disappear.”

Percy gazed at the endless horde of monsters. Even if he let Bob make this sacrifice, how could one Titan defend himself against so many for twelve minutes, all while keeping his finger on a button?

The cement settled in Percy’s stomach. He had always suspected how this would end. He would have to stay behind. While Bob fended off the army, Percy would hold the elevator button and make sure Annabeth got to safety.

Somehow, he had to convince her to go without him. As long as she was safe and the Doors disappeared, he could die knowing he’d done something right.

“Percy…?” Annabeth stared at him, a suspicious edge to her voice.

She was too smart. If he met her eyes, she would see exactly what he was thinking.

“First things first,” he said. “Let’s cut those chains.”

“IAPETUS!” HYPERION BELLOWED. “Well, well. I thought you were hiding under a cleaning bucket somewhere.”

Bob lumbered forward, scowling. “I was not hiding.”

Percy crept toward the right side of the Doors. Annabeth sneaked toward the left. The Titans gave no sign of noticing them, but Percy took no chances. He kept Riptide in pen form. He crouched low, stepping as quietly as possible. The lesser monsters kept a respectful distance from the Titans, so there was enough empty space to maneuver around the Doors; but Percy was keenly aware of the snarling mob at his back.

Annabeth had decided to take the side Hyperion was guarding, on the theory that Hyperion was more likely to sense Percy. After all, Percy was the last one to have killed him in the mortal world. That was fine with Percy. After being in Tartarus for so long, he could barely look at Hyperion’s burning golden armor without getting spots in his eyes.

On Percy’s side of the Doors, Krios stood dark and silent, his ram’s-headed helmet covering his face. He kept one foot planted on the chain’s anchor and his thumb on the UP button.

Bob faced his brethren. He planted his spear and tried to look as fierce as possible with a kitten on his shoulder. “Hyperion and Krios. I remember you both.”

“Do you, Iapetus?” The golden Titan laughed, glancing at Krios to share the joke. “Well, that’s good to know! I heard Percy Jackson turned you into a brainwashed scullery maid. What did he rename you…Betty?”

“Bob,” snarled Bob.

“Well, it’s about time you showed up, Bob. Krios and I have been stuck here for weeks—”

“Hours,” Krios corrected, his voice a deep rumble inside his helmet.

“Whatever!” Hyperion said. “It’s boring work, guarding these doors, shuffling monsters through at Gaea’s orders. Krios, what’s our next group, anyway?”

“Double Red,” said Krios.

Hyperion sighed. The flames glowed hotter across his shoulders. “Double Red. Why do we go from A-22 to Double Red? What kind of system is that?” He glared at Bob. “This is no job for me—the Lord of Light! Titan of the East! Master of Dawn! Why am I forced to wait in the darkness while the giants go into battle and get all the glory? Now, Krios I can understand—”

“I get all the worst assignments,” Krios muttered, his thumb still on the button.

“But me?” Hyperion said. “Ridiculous! This should be your job, Iapetus. Here, take my place for a while.”

Bob stared at the Doors, but his gaze was distant—lost in the past. “The four of us held down our father, Ouranos,” he remembered. “Koios, and me, and the two of you. Kronos promised us mastery of the four corners of the earth for helping with the murder.”

“Indeed,” Hyperion said. “And I was happy to do it! I would’ve wielded the scythe myself if I’d had the chance! But you, Bob…you were always conflicted about that killing, weren’t you? The soft Titan of the West, soft as the sunset! Why our parents named you the Piercer, I will never know. More like the Whimper.”

Percy reached the anchor hook. He uncapped his pen and Riptide grew to full length. Krios didn’t react. His attention was firmly fixed on Bob, who had just leveled the point of his spear at Hyperion’s chest.

“I can still pierce,” Bob said, his voice low and even. “You brag too much, Hyperion. You are bright and fiery, but Percy Jackson defeated you anyway. I hear you became a nice tree in Central Park.”

Hyperion’s eyes smoldered. “Careful, brother.”

“At least a janitor’s work is honest,” Bob said. “I clean up after others. I leave the palace better than I found it. But you…you do not care what messes you make. You followed Kronos blindly. Now you take orders from Gaea.”

“She is our mother!” Hyperion bellowed.

“She did not wake for our war on Olympus,” Bob recalled. “She favors her second brood, the giants.”

Krios grunted. “That’s true enough. The children of the pit.”