Olympus shone with a golden splendor as Percy stepped out of the elevator in the clouds. Olympus looked nothing like it did last summer when Kronos attacked New York City. Percy shivered at the memories of last summer, when Kronos was defeated and his once friend Luke was killed. Percy walked down the golden pathway leading to the main palace. He saw all the nymphs and spirits looking and pointing.

"Percy Jacksons back!" they cried. "Percy Jacksons back!"

Percy walked through the gate of the Olympian palace and took a deep breath. He opened the doors and stepped into the throne room. A few gods, his father included, were lounging around, before they notice him. Ares was the first one to notice.

"Well, well, well, if it isn't my pal Percy." He said with mocking sarcasm in his voice. Percy stiffened. They've been very discreet around each other over the last few years. Poseidon, his father, gave a beaming smile.

"Percy, my son!" Poseidon rose from his throne and shrunk to regular size to greet him.

"Hello, Dad." Percy said, smiling.

"How was this year?" Poseidon said, giving Percy a pat on the shoulders.

"Good," Percy said gingerly. "No monsters."

Poseidon gave a weak smile to that. "Excellent," he said.

Percy glanced at the other gods. Hermes was arguing with his snakes, Martha and Bob. Aphrodite was brushing out her hair, and when she saw Percy looking she gave a cute wink (Percy blushed!), Ares was picking his teeth with his pocket knife, and Apollo was staring down at his lyre with a gloomy face. Percy took note that he wasn't his usual giddy self.

"Well, my boy, you're probably wondering why you're here." Poseidon interrupted his thoughts, and guided him down a long corridor. "I have a special task for you, and I believe you are the only one who can do it." He brought Percy to a small room with only two chairs, a sofa, and a fireplace. The walls were a deep green and it looked like it hadn't been used ever.

"Sit down, son." Poseidon instructed. Percy obeyed and sat on one of the chairs. Poseidon sat on the opposite one.

"Perseus," Poseidon said softly. "I need you to rescue your sister and bring her to Olympus."

Percy stiffened when his dad said his real name. "Who's my sister? I don't have a sister!" Percy almost yelled. "Can you at least explain to me?"

Poseidon sighed. "Your half-sister really, I had her with another woman." He began. "She should be over 100 years old by now, but I'm almost positive that she was preserved at the age she was…kidnapped. 18."

Percy sat silently. After a few moments he asked, "What was her name?"

"Odette," Poseidon answered quietly, almost like a prayer. "Odette Daaé."

Percy thought to himself. Okay, she's not my full sister, so Mom wasn't keeping anything from me. Her name is Odette, which sounds like a pretty old name and Dad said she's over 100 years old so I'm guessing she was born before the agreement of the Three Brothers, and Dad sounds like he really cares for her. Got it.

"Go on, please." Percy moved forward in his chair.

"Her mother was a young woman named Emillie. She was by far, the most beautiful woman at the time. I met her in France, where the light was at its brightest, in the mid 1860's. We met and fell in love, and she had Odette. At this time, the Titans started to stir a little, and I had to leave to straighten things in the sea where Oceanus resided. Emillie met a young man named Gerard, so I wasn't worried that Emillie and Odette would be alone. Even though I was sad, I left. Before I left I explained to Emillie what was going on and I instructed her to tell Gerard nothing, nothing but to act as a father to Odette and a husband to her. I never saw her again. I later learned that she died when Odette was small and Gerard grew sick and died too. I watched over Odette invisibly to her eyes. She was taken to the city of Paris, where she was adopted by her 'father's friend, Madame Valerius. She became a ballerina in the Paris Opera House, at age eight. I was the proudest father in the world…" Poseidon took a few moments to rest.

"She grew up in the ballerina dormitories, and tried to pursue a career as a prima dona ballerina. But I knew she always loved to sing. Her "Papa", as she called Gerard, was a skilled violinist and singer. He taught her at a young age to sing and she was amazing at it! But, when he died, she lost her interest in singing and it faded. Then, she started to hear a strange voice in her dressing room. The voice was so lovely; she knew it could only be the ghost of her father. I knew it couldn't be, for I made sure that Hades allowed Gerard into Elysium for being the father of my child, but he could never leave. I also made sure that Emillie went there, too. This 'Angel of Music' as she called it, brought back the life in her voice and she became a superior singer. She took the lead one night in an opera. Later she disappeared. And she wasn't seen again."

Percy knit his eyebrows in confusion. "But you said you know where─"

"I do know where she is," Poseidon interjected. "She was kidnapped by her 'Angel of Music'. But he was no Angel. He was Erebus, the god of darkness, son of Hades and Persephone. He was rejected from his mother at birth because he had a gruesome disfigurement on his face. He tried to conceal his ugliness behind a mask, but Persephone just saw him as a monster. He left the Underworld and tried to live among mortals, but even they rejected him. So he built a house under the Paris Opera House, and never walked the earth again. He made mischief all the time, and was soon referred to the company as the 'Opera Ghost'. When Odette joined the company at the ballet, he heard her singing, and he thought that he could teach Odette to bring the life back into her voice. He began to sing and teach to her through the mirror in her dressing room. When she was taught enough, he made sure that the lead singer for that night's opera called in 'sick', and Odette took the lead. When young suitors tried to court and seduce her, he grew jealous with rage and abducted her. A young man who admired her followed him into the abyss, trying to find Odette. He found Erebus' secret lair, and begged that he'd let her go…"

Poseidon sat back in his chair, obviously pained by the story. "Percy," he said. "Do you think it's right if gods falls in love with a mere demigod such as her?"

Percy gave Poseidon a confused look. "You said gods, with an s. I thought you said…" Then it hit him. "The man who went down after her wasn't really a man? He was another god?"

"Yes Percy, he was a god, and a more powerful one, too." He smiled, obviously pleased that Percy caught that. "You've met him before, Percy, think."

Percy sat back in his chair. Odette loved music, Erebus was a darkness freak, and the opposite of dark is…

"Apollo." He said. "God of light and music."

"Well done, Percy!" Poseidon praised him. "Yes, the god of the sun had fallen in love with my daughter."

"So obviously Apollo failed getting Odette because she's still in his lair─"

"No, not anymore," Poseidon said. "Well, yes, Apollo failed, but since we had to move to America because the light was changing, they had to go, too."

"So is she in the Underworld?" Percy asked. Poseidon sighed. "She might be," he said. "But she might also be under a famous musical landmark in the city, knowing Erebus."

"And that's…?"

"Carnegie Hall."

Percy heard that place before. He and his mom passed it one day in the city, trying to find him a new school. Carnegie Hall was for all those rich people who just wanted to hear music for 4 hours straight.

"What should I do, Dad?"

Poseidon smiled. "Go back to camp, pick your followers tonight, then come back to the city to Carnegie Hall. If she isn't there try the Underworld. Use Orpheus' entrance in Central Park."

"What if she isn't?" Percy asked.

"Then you will search, and search until you find her. Percy, I know this isn't as important as your other quests, but it's important to me, and I'm sure Apollo thinks it's important, too."

Percy wringed his hands. "What does Apollo want with her? I mean, shouldn't of he forgotten about her by now or something?"

"Apollo fell for Odette when he heard her sing at the Opera. He had never seen musical perfection such as hers'. They began to meet in secret, after Odette explained about her Angel of Music. Apollo didn't believe in such thing and threatened to challenge her Angel. Odette pleaded him not to, and promised to run away with him after her performance the next night. But, what they didn't know was that Erebus had been listening from the shadows of their plan, so that's why he abducted her the next night. To prevent that from happening." He sighed. "She really did love Apollo. And Apollo did really love her, more than any mere mortal or demigod."

"Oh," Percy said softly, obviously not interested in the mushy gushy love story. "So why does Apollo want her now? Like, when she was abducted, why didn't he send everyone down to find her? That doesn't seem right, if he loved her so much as you say, and just abandoned her."

"I thought the same thing when I learned of her abduction." Poseidon said. "I was furious when Apollo didn't do anything. He did send Hermes down to the Underworld once to persuade Erebus to free her, but Erebus refused. Apollo can't bear to go to the Underworld. There's no sunlight, so it's not his realm. But if she came up here, then everything would be good. Lately Apollo has been moping around the palace, yearning for her. I can't bear to see anyone in that state, and I really want to meet one of my few daughters. Please Percy, please do this for me. And," Poseidon said meekly. "I really want you to meet her, too."

Percy whispered, "Is Erebus…?"

"No, I believe, he isn't a follower of Kronos." Poseidon confirmed. "He may be a mad man, but he isn't evil."

Percy sat in silence and basked in the info. "Okay," he said. "I accept."

"Excellent!" Poseidon beamed. "I'll escort you to the elevator."