Rick Riordan owns characters.

Pertemis story. Percy and Zoe are brother and sister. Nico and Bianca are the same age.

The story starts right after Nico and Bianca are sent to camp after Annabeth is taken to Mount Othrys to hold the sky as bait for Artemis.

Nico sat down next to Grover after breakfast, watching the Satyrs chase the Nymphs, unsuccessfully. Nico told Grover of his gripes with the Hunters of Artemis, after his sister decided to join The Hunt, instead of stay at camp with him.

"Well, she shouldn't be in danger anytime soon," Grover said, trying to calm Nico down.

"Wait, why not?"

"I may have heard an argument between Zoe and Argus this morning. Something about needing to leave camp."

Nico's eyes narrowed, "How does that equate to them not leaving? If anything it sounds like they're leaving pretty soon."

"No. I guess Chiron heard their argument too, because he came out in pajamas and his horse tail in curlers and-"

"He wears curlers in his tail?"

"Yeah, but that's not the point, "Grover continued. "The point, is that Chiron told her that she's supposed to stay at camp until they received orders from Artemis."

Nico, still not getting the point, furrowed his eyebrows. "So what's the problem?"

Grover sighed, "The problem what she said after; she said 'How are we to get orders from Artemis if Artemis is lost?'"

"What do you mean lost? Like she needs Directions?"

"No. I think she meant gone. Taken. Kidnapped."

"Kidnapped?" Nico's brain went into overdrive. How would you even kidnap an immortal goddess? Is that even possible? And if she was kidnapped so easily, how safe would Bianca be with them? Nico's ADHD kicked in, "Hey Grover, how did you overhear this conversation?"

Grover blushed. "I was sort of camped outside the Artemis cabin."

Nico couldn't contain his laughter at that.

Later that night was capture the flag against the Hunters. Since it was winter break, most of the campers had gone home, so it was a small game. Only 13 Hunters, including Nico's sister, Bianca, and about the same number of campers.

The flag was set at the top of Zeus's Fist, though Nico argued it looked more like a Poop Pile than a Zeus's Fist, but Chiron stomped that idea quickly. On guard duty with Beckendorf and the Stoll brothers, was Nico. He was decked out in a blue-feathered bronze helmet that was falling into his eyes, and his breastplate was about six sizes too big.

Unsurprisingly the Hunters won, Bianca was on defense opposite her brother, while Zoe grabbed the flag. Thalia was still arguing that she could have grabbed the flag and won, had some Laurel girl not gotten in her way.

Grover walked over to Nico as he was taking his armor off. "Good game, Nico!"

"Grover, we lost, Zoe kicked our butts."

"Yah, but that was only your first game, you'll get 'em next time."

"I highly doubt that, but tha-" Nico stopped talking as he saw someone . . . something approaching. It was shrouded in a murky green mist, but as it got closer, the campers and Hunters gasped.

"This is impossible," Chiron said. He'd never sounded so nervous to Nico before. "It . . . she has never left the attic. Never."

And yet, the withered mummy that held the Oracle shuffled forward until she stood in the center of the group. Mist circled around their feet, turning the snow a sickly shade of green.

None dared move. Then her voice hissed inside their heads.

I am the spirit of Delphi, the voice said. Speaker of the Prophecies of Phoebus Apollo, slayer of the mighty Python.

The Oracle regarded Nico with its cold, dead eyes. Then she turned unmistakably towards Zoe Nightshade. Approach, Seeker, and ask.

Zoe swallowed. "What must I do to help my goddess?"

The Oracle's mouth opened, and green mist poured out.

Nico saw the vague image of a mountain, and a girl standing at the barren peak. It was Artemis, but she was wrapped in chains, fettered to the rocks. She was kneeling, her hands raised as if to fend off the attacker, and it looked like she was in pain. The Oracle spoke:

Five shall go west to the goddess in chains,

One shall be lost in the land without rain,

The bane of Olympus shows the trail,

Campers and Hunters combined prevail,

The Titan's curse must one withstand,

And one shall perish by a parent's hand.

Zoe picked up a cheese ball from the Ping-Pong table, examining it as if were her prey. "I would prefer to take all the Hunters, we will need strength in numbers." She continued staring down the snack.

The room was filled with head counselors of each cabin, a few hunters, Chiron, and Dionysus. The Stoll brothers, Silena, Beckendorf, Thalia, Nico, Bianca, and Zoe to name a few.

"The prophecy calls for five, as well as being a combination of hunters and campers. Unless you wish to fail to save Lady Artemis, I think it best to follow the prophecy to the letter."

Obviously, Zoe was not very happy with that, but she followed the advice anyway. "I shall go, of course, and I will take Phoebe. She is our best tracker." Everyone nodded at that. "And I wish Bianca to go."

Bianca looked stunned. "Me? But . . . I'm so new. I wouldn't be any good."

Nico nodded in agreement. "Exactly, I should go instead, she's my sister and shouldn't be put in danger so soon."

Chiron raised an eyebrow. "We could say the same thing to you, my boy."

"It doesn't matter, Bianca will be fine," Zoe insisted. "There is no better way to prove thyself. And I will not be traveling with a boy."

"I'll go." Thalia stood and looked around, daring anyone to question her.

Zoe nodded. "And one more."

"Me!" Grover stood up so fast he bumped the Ping-Pong table. He brushed cracker crumbs and Ping-Pong ball scraps off his lab. "Anything to help Artemis!"

Zoe wrinkled her nose. "I think not satyr. As I stated before, I will not be traveling with a boy, and you are not even a half-blood."

"But he is a camper," Thalia said. "And he's got a satyr's senses and woodland magic. Can you play a tracker's song yet, Grover?"

"Absolutely!"

"So be it." Chiron said. "Thalia and Grover will accompany Zoe, Bianca, and Phoebe. You shall leave at first light. And may the gods" -he glanced at Dionysus-"present company included, we hope- be with you."

A boy was hunkered down behind a Greek column, like he was hiding from someone.

This boy was Nico, it wasn't even dawn yet. Nowhere near time for breakfast. It seemed as though he were taking a page out of Grover's book, and spying on the Hunters.

"I don't think I should leave Nico just yet. He only just got here, and we've been together for our whole lives"

Zoe nodded in understanding. "I get that, Bianca, I do, but we need you. We need five for the quest, and I chose you for this quest. Your brother will be here when come back to get the rest of the hunters."

Bianca stared at her wide-eyed. "But you don't get it! He's my brother, I should be here to protect him for the time being."

"Enough! You will be going on this quest. You can say goodbye to him before we leave. You are needed on this quest, I can feel it. Just trust me on this, Bianca. You will make it back, okay?"

Bianca looked unsure, but nodded anyway.

Nico just stared at the two of them. He didn't care whether they didn't want him going along, he was going to protect his sister no matter the consequences. They didn't survive against the Manticore to just die now. He made his decision, he would take Annabeth's invisible cap and shadow the group.