Leo Valdez was asleep in his cot aboard the Argo II, dreaming of a silhouette engulfed in flames.

The heat was intense, but it didn't bother Leo. As the only son of Hephaestus, the fire god, born with power over fire, he wasn't even fazed by the flames lapping at his face. Still, his dream-self took a hesitant step forward, for he had yet to discover the limits of his flame-resistant abilities. But he looked up at the figure in front of him, thinking, Who is that?, and broke into a run.

"Hey!" called Leo. "You need to get out of here! The fire's getting out of control!"

The figure turned, and Leo gasped.

Leo jolted awake in a cold sweat. Man, demigod dreams suck, he thought. And they always end at the important part.

He climbed out of bed and strode over to the porthole on the side of his cabin. A full moon shone down on the starboard deck. "Wonder how upset Coach Hedge would get if I snuck out for a late-night walk," he said aloud. "He was pretty darn mad after the Percy/Annabeth incident." He chuckled, remembering how Frank had found those two asleep in the pegasus stables. "Oh well. I'll take the risk. Won't be able to sleep after that." He walked through the door, down a small, dark corridor, his only light a small fire in his hand.

He crept past Jason's cabin, past Frank's, past Percy's, then finally past Coach Hedge. Coach's satyr ears made sneaking around difficult, but judging by the way he was snoring, Festus—the Argo II's mechanical bronze dragon figurehead—could've set off all the alarms, and Hedge would still be sleeping.

Leo walked over to the port-side rail, looking down at the dark blue waters of the Mediterranean Sea gliding over the hull. It was July thirtieth, and the crew was sailing toward Greece to go defeat Gaea and her plans to destroy mankind. It was about three weeks ago that they had closed the Doors of Death, and they had two more day before Gaea awoke fully. They were so close to sailing home—Leo, Piper, Percy, & Annabeth to Camp Half-Blood; Jason, Hazel, & Frank to Camp Jupiter.

Camp Half-Blood. Home.

Leo hadn't had any real home since he was eight years old, before Gaea had killed his mom in that machine-shop fire. After years of bouncing around from foster home to foster home, boarding school to boarding school, he had finally found a place to call home.

His thoughts drifted to the figure in his dream.

From what Leo had seen, the figure was a girl. He hadn't been able to make out many details, but she had really long, curly hair, a Greek chiton, and a tool belt around her waist. (Which didn't really go well with the chiton, but hey, whatever.) Maybe she was a minor goddess with fire-resistant powers—one who served his dad, Hephaestus. The chiton had to be some sort of clue to that, right?

Leo squinted. Was it just his imagination, or was the sun coming up…?

Nope. That was definitely the sun. How long had he been standing there? Suddenly he could feel the chill of the sea spray on his bare chest. He'd been so lost in thought, he hadn't even remembered to put a shirt on.

Too quickly, the memory of Calypso's Island came back to him. He remembered making a seeing device that had combusted, sending a flash fire up his arm. Remembered how beautiful Calypso's singing was, how he had been staring like an idiot the whole time. How beautiful she was.…He shook his head. Keep moving, he told himself. That was his motto; it had been ever since his mom died, since he'd run away from his Aunt Rosa in a desperate attempt to get away from the guilt of killing his mom with his powers. He didn't like to dwell on things that he couldn't get back.

But he couldn't think like that. He'd sworn on the River Styx that he would free Calypso of her curse. She had told him not to give her yet another empty promise—she had enough of those to last an entire century. He'd started to answer, "How about a full promise?" when she kissed him.

He touched his lips. The tingle of his first kiss still lingered—which only reminded him of the reckless oath he made.

Seven half-bloods shall answer the call.

To storm or fire, the world must fall.

An oath to keep with a final breath,

And foes bear arms to the Doors of Death.

The Great Prophecy, or the Prophecy of Seven, scared him more than he let on. Especially the line about the oath—An oath to keep with a final breath. Couldit be about his promise to Calypso? He didn't want to die, but he didn't wish for Calypso's death, either. Was a goddess even able to die? He didn't want to find out.

"Leo? How long have you been awake?"

Leo turned to see Piper, rubbing her eyes sleepily. "Oh…Hey, Piper. I don't know, a couple of hours? I had one of those stupid demigod dreams."

"Well, can you go put on a shirt?"

He cracked a smile. "Aw, man, do I have to? The sea spray sure feels good. Why don't you try?"

"Leo Valdez! Go put on a shirt, now!" Piper commanded, deliberately using her charmspeak.

Leo automatically started in the direction of his cabin. "Man, I hate when you do that." But he continued walking against his will, so he decided to just give in. He knew from experience that fighting it was useless.

Leo was putting on his favorite outfit, an army fatigue jacket over a white T-shirt and jeans. Well, a replica of his favorite outfit, actually, since the original had burned up months ago. The fabric was woven out of fireproof materials, and it stayed clean no matter what. Calypso had made it for him on her loom; along with a small pouch of the same fabric, which he had given to Frank to keep his lifeline—a piece of highly flammable driftwood—safe.

Leo pressed the T-shirt against his face. He could still smell Calypso's sweet cinnamon scent in the fabric. He smiled sadly. He wanted—needed—to see her again. And he would; he would, no matter what happened along the way.

Suddenly there was a knock on his door. He quickly pulled the shirt on and went to open the door. "Oh, Hazel. Hi. What's up?"

Hazel shifted from foot to foot. "Aren't you going to eat?" she asked. "You've been in here for thirty minutes, and you're needed on deck."

"Oh. Okay. I'll be right there." He shut the door in her face, once again lost in thought.

Leo walked over to his bedside table and opened the drawer. Inside was an old-fashioned astrolabe, an item that he'd found when dealing with the Kerkopes, a pair of monkey-like dwarfs that liked to steal shiny things. Odysseus had made it, apparently to find Ogygia, the island where Calypso was trapped. Supposedly the only thing that was missing was a crystal from her cave—which Leo had succeeded in getting—now he just needed to figure out how to get the astrolabe working.

Then he realized his stomach was growling, and he decided he should go get some breakfast.

"So Leo," said Piper as he walked into the mess hall, "may I ask you about that 'stupid demigod dream' you had?"

Leo shrugged as he grabbed a plate from the cupboard. "To be honest," he said, "it wasn't really 'stupid,' just…confusing."

"What's confusing?"

Leo turned to see Jason and the others filing into the room. "Uh…a dream I had last night," he answered, suddenly uncomfortable.

"Do you want to talk about it?" Hazel asked, obviously worried.

"Yeah, sure. I guess." He sat down heavily. Churros—braided pieces of bread sprinkled with cinnamon and sugar—appeared on the plate, making him smile. The Mexican treat brought back good memories, reminding him of when his mother was alive. That sweet cinnamon scent made him think of his abuela's place, and…

And Calypso.

His smile melted. Then he remembered that the others were watching him expectantly, waiting for him to explain his dream. "Uh, it was about a…a girl…standing in the middle of a…of a fire," he stuttered.

Everyone stared at him.

"A girl," Annabeth said dubiously. "In the middle of a fire."

"Uh, y-yeah."

Piper was the first to recover her composure. "Well, what did she look like?"

"Um, she had really, really long, curly hair. And she was wearing a Greek chiton. And a tool belt."

Percy knit his eyebrows. "A chiton and a tool belt? That's certainly an interesting fashion statement," he said, trying to lighten the mood. Leo frowned. Wasn't that his job?

"Um, uh, well, the thing is, she seemed familiar," Leo said, still strangely uncomfortable. "Look, guys, I only got like two hours of sleep, and I'm hungry. Can we not talk about this anymore?" he said, suddenly upset.

His friends, surprised at his sudden outburst, blinked and said, "Okay, sure."

"Thanks."

The churros tasted like sawdust in Leo's mouth. The happy feelings they once brought were now replaced with the heartsickness that came with the memory of Calypso.

I need to get her out of my mind, Leo thought. At least for the time being.

He looked up at the wall, where a live view of Camp Half-Blood was displayed. This time it showed the basketball court. There wasn't anyone there, which kind of confused Leo. It was around noon or so on Long Island, so there should've been campers everywhere—but the commons area was deserted.

Then the image rippled, and suddenly there was a girl standing on the court—the girl from his dream. Leo gasped.

She was staring right at him.

"That…that shouldn't be possible.…" he whispered. "There's no way she can see me.…"

Everyone looked at him, their expressions showing concern. They all turned to the wall…but they remained confused.

"Leo?" said Annabeth. "What's wrong? What do you see?"

"You don't see her?" Leo said. Was he having a vision? Or was he going crazy? A vision, he decided. That makes the most sense.

Then the girl spoke.

"Leo…" she breathed. "It's been so long."

"What? Who are you? I don't know you," Leo replied, sounding a little scared—but as soon as the words left his mouth, he realized he did know her…He just couldn't remember how.

The girl whirled around as a column of fire started to burn behind her. She turned back to Leo, panic in her eyes. "Hephaestus calls me back to Olympus. For now, I must go…But I shall be reunited with you in Greece," she said, walking backwards into the column of fire. "And know this: I have been watching over you all these years, waiting in Father's forge."

"Wait," called Leo—but she disappeared in a shower of sparks. "How do you kn—" Suddenly Leo slumped back in his chair, and lost consciousness.