Disclaimer: I don't own Percy Jackson and the Olympians, or Heroes of Olympus.

Part I

Percy and Annabeth were still alive, at least. Leo hung onto that thought as he stared through the Doors of Death at them.

Monsters surrounded his friends, stretching out for miles beyond his view. The only thing protecting them was one of Percy's signature hurricanes, but Leo had no idea where the son of Poseidon was getting the water to make a barrier that powerful, let alone the strength. He and Annabeth looked completely exhausted. There was no time to waste.

"Can you guys climb out of there?" he yelled.

Percy lifted his head. The guy had always looked alive and full of energy – a little like Leo himself – but now his eyes were dim. He shook his head. "Pull . . . of Tartarus . . . too strong . . ." he managed to shout.

"Okay!" Then Leo turned to his friends. "I'll be right back," he told them. "If any monsters break through Percy's hurricane . . . I don't know. Just stop them somehow."

"What are you going to do?" Hazel asked him. But Leo was already running out of the House of Hades.

The Argo II was waiting right outside. Leo didn't hesitate for a second; he just hopped onto the rope ladder and started climbing. Once he reached the deck, he ran downstairs into his cabin, where he had laid out supplies, just in case. He stuffed three bottles of water, a canteen of nectar, and about twenty granola bars into his tool belt. Then he strapped a Celestial bronze sword to his waist and rushed to the helm.

"Does it work?" he asked Festus anxiously. "The project?"

Festus's teeth clicked and whirred. Of course it does.

Leo breathed a sigh of relief. "Good. All right, then. Festus, we're going inside!" The dragon clicked and whirred some more. "Yes, through the doors," Leo said impatiently. "What did you think? No, I don't care if you have to break the doorframe a little. We need to get in there!"

Festus must have picked up on Leo's urgency. Without another protest, he turned towards the doors. Leo toggled the control stick on his Nunchuk and shook his Wii remote. The Argo II zoomed towards the House of Hades, and with a crack that must have echoed through all of Greece, it shoved its way inside.

"Leo!" the others shouted in amazement. "What are you doing?"

Leo didn't waste time with words. He just tilted his Wii remote and yanked a couple levers, so that the ship faced the Doors of Death head-on. The pull of Tartarus was pretty strong, even from this distance, but the ship was unfazed. Leo had been counting on that.

"Percy! Annabeth!" he yelled. "I'm going to get you guys out of there! Just hold on!"

Annabeth was barely conscious, and all of her remaining strength was focused on keeping her hand plastered to her shoulder so that as little blood as possible leaked out. Percy looked just as bad off, if not worse – his injury was at his side, not his shoulder – but he somehow managed to hear Leo. He squinted through the pain and saw the bronze dragon figurehead. "No, Leo!" he shouted. "You can't get us both! The Doors have to be closed from both sides! I have . . . to stay behind!" Percy didn't want to be stuck in Tartarus forever – he'd been waiting for his happily-ever-after with Annabeth for too long – but he also didn't want anyone else to be. If Leo pulled him out now, Percy knew he wouldn't be brave enough to go back to Tartarus a second time by choice. But the Doors had to be closed. This was the only way.

"What was that?" Leo asked. "I can't hear you, Percy! It's too loud!" In reality, Leo had heard Percy just fine. He was just choosing to ignore his words.

Percy's hurricane was starting to die out. The first monsters were slipping through the cracks, and Leo knew that as soon as one got to them, Percy and Annabeth would be finished. So he didn't wait another second. He punched a couple buttons and muttered a couple commands. A giant grabber arm shot out of the hull just underneath Festus and pushed all the way to Tartarus.

Leo's tongue stuck out as he frowned in concentration. "A little to the right," he muttered. "Farther . . . No, not that far . . ." He knew he only had one chance to get this right. Another try, and the monsters would be on top of them. "Come on, come on. . . . And . . . Perfect!" He flicked a switch, and the claws closed around his friends. He punched the air in excitement. "Yes! Now, reverse! And gently deposit cargo on the deck!" He shouted commands at Festus and pulled levers like a madman. By the time he was done, Percy and Annabeth were lying on the deck, his other friends were climbing the rope ladder to get to them, and Leo had secretly made a few adjustments to the steering mechanisms.

"Annabeth! Percy! Are you guys okay? Oh my gods, what happened to you?" Piper was babbling as she ran to them and took in their injuries. "I'll get you some nectar right away. Ambrosia too. Just a second . . ."

"Already done, Pipes," Jason interrupted, handing her a canteen.

"And here's water," Hazel added breathlessly, coming up from belowdecks. "I'm sure you guys need it. Food can come later, once you're stronger."

The others fussed over the pair, but Leo stood back nervously, eyeing the Doors of Death. They weren't closing. In fact, they seemed to be widening.

Nico was noticing the change too. He spoke up. "Guys, we have a problem." He nodded towards the Doors. Percy's hurricane had completely dissipated, and monsters were streaming through.

"I'm on it," Leo said quickly. "Festus, breathe fire." The dragon obeyed, shooting a stream of flames so hot that the monsters instinctively retreated, even those immune to fire. As soon as Leo was sure that they were safe for the moment, he ran to Percy and Annabeth. But not to comfort them. The others would have plenty of time for that later.

"Percy," he said. "Can monsters die in Tartarus?"

"Leo!" Piper said. "Why are you interrogating them? They're barely conscious!"

"I have to know," Leo said shortly. He turned back to Percy. "Well?"

"No," the son of Poseidon croaked. "They . . . get transported . . . to other parts . . . sometimes. . . . But never die."

"Okay. Can demigods?"

Percy coughed out a weak imitation of laughter. "I . . . don't know. . . . I . . . never tried . . . to find out."

"Fair enough," Leo said. "Now what do I need to close the Doors?"

Slowly, the others seemed to realize what Leo was planning. "Leo . . ." Hazel whispered. "Why do you have a sword? You never use a sword."

Leo kept his eyes on Percy. "What do I need to close the Doors?"

The older demigod looked at him, and his eyes focused. "No, man . . ." he croaked. "You can't . . ."

"Don't tell me what I can and can't do!" Leo shouted. His hair was starting to smoke, and he didn't bother putting it out. "Just tell me how to close the Doors!"

Percy hesitated. "You . . . It's not fair . . ."

"Life isn't fair, Jackson," Leo said. He couldn't believe he was being so cross with such a legendary camper, but he really didn't have any time to waste. For one thing, he wasn't sure how long he could hold his resolve. For another, it was only a matter of time before the monsters came through again.

Percy shook his head and closed his eyes. "Fine . . ." he said. "You can . . . use fire . . ."

"Good. That's all I needed to know." Leo looked at Nico. "You'll close them topside?"

Nico's eyes were unreadable, but his voice wavered when he spoke. "Leo. . . . You don't understand what it's like in there . . ."

"I do," Leo said. "It's horrible, and I might not make it out alive. In fact, I probably won't. I get it. Now, will you close the Doors topside or what?"

"Of course I will," he sighed.

Leo looked at Frank. "You guys will be happy together," he said simply. It was the only way Leo could think to apologize for screwing with their relationship by looking like Sammy.

Hazel's eyes watered. "Leo . . ." she whispered. "You don't have to . . ."

"But I do," he told her. He looked at the others. "Be safe. I'll meet up with you guys in time for the final battle . . . hopefully. If I don't . . . Well, kick Gaea's butt for me."

Piper ran to him and threw her arms around him. "Leo . . ." Somehow, she thought, this was almost worse than when Percy and Annabeth fell. This time, everyone felt like they were letting it happen. It wasn't right.

Leo disentangled himself. "Okay, okay, Pipes!" he said. "I'm going now!" He glanced at all of his friends one last time, refusing to let himself tear up. He couldn't think of any words, so he just nodded at them. "Nico, climb into the grabber arm," he said to the son of Hades.

"What?"

"The pull of Tartarus is crazy-strong," he told him. "You can't resist it and close the Doors at the same time. The grabber arm will keep you safe."

Nico hesitated. "But you . . ."

Leo shrugged. "The Doors can't close if there's a metal claw in the way. Stop arguing, Nico. Just get into it."

Finally, everyone seemed to accept that this was happening. They stared at him in shock as he ran to the helm and steered Nico in front of the Doors. Then he hurried to the rope ladder and took the rungs three at a time. The first monster had just breached the entrance.

"I'll see you later!" he shouted up at the crew, not sure if his words were lost in the general commotion. "It'll be fine!" He didn't believe that himself, but he wanted to give the others hope.

As soon as his feet touched the ground, the pull of Tartarus sucked him through the Doors.

"Leo!" Piper's piercing scream shot through all the other noise. The rest of the crew just stared, dumbfounded, as Leo struggled to his feet. He was almost exactly in the spot where Percy and Annabeth had been moments ago. He turned and sent an arc of flames towards the other monsters. It was shaped just like Percy's hurricane, and acted like the same temporary barrier. Leo wasn't sure if that was a good or bad sign.

"Are you ready?" he shouted to Nico. The son of Hades nodded. "Then let's do this!"

Leo put his hand on one of the Doors and felt the mechanism. Percy was right. It would take the incredible power of searing white fire to force this Door to meet its partner again, just like it had taken a different incredible power to open the Doors in the first place. Leo figured that, from the nature of the lock, Percy probably could have closed it if he had sent the power of a hurricane into its gears. But then Percy and Annabeth would be stuck in here, exhausted, injured, and without supplies. Leo would be stuck in here once he was done, but at least he would be full of energy, uninjured, and stocked with the things he'd stuck in his belt. Hopefully.

If Jason was down here, he probably could have summoned a storm and arced lightning into the lock to close it too, but Leo wasn't about to yell that up to the Argo II. The son of Jupiter might have felt guilty enough to try to be a hero and take Leo's place. And Leo couldn't allow that to happen – not after he'd seen how happy Piper had been for the last few months.

"All right, Nico!" Leo yelled. "I'm starting!" He touched his palm to the lock and thought fire. The mechanism just absorbed the flames. Leo knew then that closing the Doors would take all the juice he had. Now he was really glad Percy wasn't the one doing this. The effort might have just killed the worn-out demigod.

Fire, he thought again. Hotter. White-hot flames burst out of his hand and filled the lock with heat. More, he thought. Don't just fill the lock. Fill the Door. With his other hand, he reached towards the other Door and shot fire that way. Fill that Door too.

Leo had never tried to keep a sustained inferno going before. Black spots danced in his eyes. His vision started tunneling. His head pounded. His legs felt weak. But the fire kept coming. By sheer force of will, he was pulling the Doors together.

Then something occurred to him – something he had forgotten to mention. With an insane amount of effort, Leo raised his head. He could just make out Nico, using the same kind of concentration to release wave after wave of black energy. He searched beyond the son of Hades and saw the outline of the Argo II. "Can you hear me?" he yelled.

"Leo! What is it? Do you need help?" Leo had no idea who the answering voice was. There was an answering voice, and that was all that mattered.

"No! I'm . . . fine!" Leo was good at multi-tasking – he'd had practice while building the warship. But talking and shooting flames at the same time was the most difficult thing he could remember attempting. "Just . . . forgot . . . to tell you guys . . . something! Pass on . . . message . . . ?"

"Whatever you need, Leo! What is it?"

"Annabeth . . . has to . . . pilot ship now!" He paused to gather a few last shreds of energy. "Tell her . . . I modified controls . . . simpler! Notes . . . written . . . in my cabin . . . she . . . has to . . . study them . . . use Archimedes sphere . . . smartest demigod . . . she can figure it out too! I . . . trust . . . her! And . . . I . . . trust . . . you . . . all! Remember . . . don't . . . touch . . . ground . . . until final . . . battle! Gaea . . . can't get . . . other half . . . sacrifice . . . if no girl . . . ! Stay . . . safe . . . and we'll . . . win . . . ! Stay safe . . . and you'll defeat . . . Gaea . . . even . . . if . . . without . . . me!"

"Leo, you'll be fine!" the voice yelled. "You'll make it out of there! You told us so yourself!"

Leo didn't bother answering. He knew as well as the voice did how likely that was. Besides, he had to focus all of his energy on closing the Doors now.

Slowly, slowly, the Doors moved together. The strain was literally killing Leo. He saw his life flash before his eyes. Sitting on his mom's knee, tapping out Morse code in the workshop. Kneeling in front of the ashes of that same workshop. Running away from his first foster home. Running away from the second. Running away from countless others. Modifying Coach Hedge's megaphone. Laughing with Jason and Piper. Finding Camp Half-Blood. Defeating Ma Gasket. Defeating Khione. Returning to camp. Finding a new family. Finding a new home. Building the Argo II. Finding the Romans. Standing on a rock with Hazel. Standing on a limestone beach with Echo. Reaching Rome. Losing Percy and Annabeth. Reconciling with Frank. Growing closer to his crew mates. Discovering that they were friends. Finding the House of Hades. Finding Percy and Annabeth. Saving his friends. Purposefully falling into Tartarus. Saving his friends. Protecting his friends.

Leo breathed in and out slowly, trying not to pass out. He had to protect his friends. He had to be able to close these stupid Doors.

With a jolt of surprise, Leo realized that the stupid Doors were only two feet apart now, instead of twenty. "You can do this, Valdez," he muttered. "Don't back down now." And he sent one huge burst of flames out of his hands, his hair, his entire body. The heat soaked into the Doors of Death, destroying the final remnants of dark magic that were keeping them open. Leo fell to his knees, completely spent, and forced himself to shoot two last fires towards them. At the same time, Nico threw two massive balls of black energy. Those missiles collided, and their combined strength was just enough to finish the job. The Doors of Death slammed shut.

There was a globe perched on the top of the House of Hades. It represented that all people in the world would eventually find themselves in the god's domain. It had a sort of special power, a little like the Athena Parthenos. The globe hadn't even budged when Leo had forced the Argo II through the too-small entrance and into the building, but the power involved in closing the Doors of Death was too much for the globe to handle. As soon as Leo had finished closing the Doors for good, it toppled off its pedestal.

The rest of the seven had been busy forcing fluids into Percy and Annabeth and trying not to think about Leo's sacrifice, but when the world hit the floor outside with a thud strong enough to start a minor earthquake, their eyes all widened.

"Oh my gods . . ." Piper whispered. "To storm or fire, the world must fall. Leo used fire to close the Doors, and then that globe fell to the ground. . . . The prophecy is coming—"

"No!" Hazel shouted suddenly, her eyes filling with tears. The others turned to her in confusion. "It can't be coming true!" she insisted. "It can't be! Because the . . . the next line is . . ." She swallowed a sob. "An oath to keep with a final breath . . . And . . . And Leo promised Nemesis that he would get revenge on Gaea. And he promised that he would rescue Percy and Annabeth from Tartarus. Oh, gods, you don't think . . ." She buried her head in Frank's chest. "Nico, Leo's not dead, is he?"

Silence was her only answer. "Nico . . . ?" The others looked around and saw him, flopped across the claw arm, pale and unconscious. Everyone wanted to help the son of Hades, but they still felt too shocked to move.

Eventually it fell to Jason. He went to the helm, half-dazed, and stared blankly at the controls. Naturally, none of them were labeled. He hesitated for a moment, and then just turned to Festus. "Look, buddy," he muttered, too softly for the others to hear, "I know I'm not Leo. None of us is Leo. We don't know this ship like he does. But he's . . . he's gone now. So just until Annabeth recovers and can help us figure you out. . . . Do you think you could cut us some slack?" Festus's teeth whirled. Jason decided to take that as a yes. "Great. Then could you bring Nico over here and put him on the deck?" Obediently, the grabber arm started to move. It maneuvered over the son of Jupiter's head and deposited Nico on the floor. Immediately, Hazel ran to him and started forcing nectar into his mouth too. The others stayed crouched over Percy and Annabeth, willing at least one of them to wake up again. Jason hesitated for a split-second, and then thanked the bronze dragon figurehead before rushing over to the son of Hades.

"Closing the Doors of Death must have taken all of his strength," Hazel whispered, wiping away her tears. "He'll be fine, but he won't be waking up any time soon." Frank came over and wrapped his arms around her, and she leaned into him for comfort. Jason went to Piper and did the same. They ended up in a contorted circle made up of four points – Percy and Annabeth, Jason and Piper, Frank and Hazel, and Nico.

Neither couple said what was on their minds. With Nico unconscious, there was no way to know how Leo was doing. And . . . well, they were looking at the three people passed out at their feet. Percy and Annabeth were injured and exhausted from trekking through Tartarus and finding an exit. Nico was exhausted from closing the Doors topside. Both of those were terrible ordeals.

However, Leo had just spent at least as much energy to close the Doors from Tartarus. And assuming that he was still conscious, it would take him at least a week – that was how long Percy and Annabeth had taken, working together – to find another exit (assuming that there was another exit). Nico's fight had knocked him unconscious. Percy's and Annabeth's fights had knocked them unconscious. But Leo was facing both. That was an insane amount of danger. With the odds stacked against him like that . . . How could the son of Hephaestus possibly survive?

So even though I had this Leo-closes-the-Doors idea before I even knew about Viria, I still feel like I should credit her because her story-comic-thing was the reason that I felt confident enough to start posting this story because somebody else shared my weird headcanon! So yay, Viria rocks! But I'm pretty sure everyone knew that already. :P

Hope everyone enjoyed the chapter! Tell me what you thought!