I do not own Percy Jackson and the Olympians or The Heroes of Olympus. They belong to Rick Riordan.

By the time they reached the city's end, they had lost the silent maniac with the sword.

"Ugh!" Thalia growled. "Now that jerk could be anywhere, and it's not like we can just stay here and scour the entire place!"

"I don't think we need to worry about it. His goal was to get our attention. Why else would he have left after leading us on?" Annabeth considered.

"That's true," Hazel agreed, "but we still can't leave without Percy."

"I'm here," grunted a welcome voice.

"Percy!" Annabeth ran up to him and embraced him tightly. He hugged her back awkwardly. "Where have you been?"

"I've..," he hesitated, "been trying to find my way around. The quakes were pretty distracting."

"I'm glad you're safe." Annabeth said. His clothes were wrinkled, his hair was messed up, and he was sweaty, but that didn't matter to her. She was just relieved to see him.

"We've been here too long," Percy said, letting her go. "Hazel, take us to the mine."

The entrance to the abandoned mine was cold and drafty. The place was perfect for the god of darkness and shadows.

"This is as far as I go. I don't know what to tell you but to be on your guard and follow the path inside," Hazel suggested. Waving good-bye, she departed.

Thalia grumbled, "I'm tired of dark and damp places." With that, they entered.

Taking out the lantern given to them by Lucia, they stumbled along the passage. All three of them had to duck multiple times to avoid bunmping into the ceiling. Annabeth sighed. Not too long ago, they had headed up a mountain. Now they traversed the underground. She had to agree with Thalia; she grew weary of dark places where monsters could jump out at any moment. As if on cue, a non-human cackle interrupted her thoughts.

A humanoid wearing green garbs dropped in front of them and hopped around. It had paper covering its face with strange markings on it. The thing skipped towards them, and Percy uncapped Riptide. He ran it through the stomach, pulled his sword out, and slashed at its neck. With a screech, it fell backwards and faded.

"That didn't look like any Greek monster," Annabeth said, confused.

"It was an imp," Percy said. "There must be more of them further on, and they don't have Greek origins.

Getting suspicious, she narrowed her eyes. How did he know that when she didn't? Before she could voice her thoughts, though, three green imps tumbled out of nowhere. Annabeth aimed a kick at one's head in front of her, and it fell sideways with a satisfying CRACK! She attempted to stab it, but it hopped back up and shot a projectile with a blowgun of sorts. Using quick reflexes, she deflected it with her dagger. She sliced twice at its abdomen, and it cried out, vanishing as it did so. Looking around, she noticed that Percy and Thalia had finished off the other two. "How did you beat them?" Annabeth asked curiously.

Percy just shrugged, and Thalia said smugly, "I hit it with brute force. Those things are wimps!"

"They'll become pests if we let them. Can we hurry up and press on now?" Percy said impatiently.

"Well, someone's a bit grumpy today," Thalia griped. Even so, she led them forward, where more stairs waited.

As they descended quietly, Annabeth attempted to start a conversation (interrogation). "Hey, Percy," she said cautiously.

"What?" he snapped irritably.

She paused, but she figured that it had to be said. "Why do you sound so bitter lately? What happened to the sweet and funny guy that we used to hang out with?"

The temperature seemed to drop several degrees, and the atmosphere immediately grew tense. Through her peripheral vision, she noticed Thalia wince slightly.

Percy thankfully remained calm, but his response hit her hard. "Maybe you didn't know me as well as you thought you did."

What? That wasn't possible…was it?

Thalia exclaimed, "Of course we know you, Seaweed Brain! We've been your friends for years!"

Annabeth nodded fervently. What was wrong with him? However, his next words put her into even greater shock.

"Pathetic. You guys of all people should know what "friends" are like. They get close, and when you're at your weakest…they stab you in the back."

Memories of Luke suddenly rushed back to her, and she almost stumbled back. Tears prickled at her eyes. Percy was her dependable, caring boyfriend. He was her rock! She didn't understand why he was saying these things.

Apparently, Thalia didn't either. "You shouldn't say that," Thalia objected. "What about all those people from camp? We fought together, and some even died!"

"They won't last long," he replied coldly.

Holding back a sob, Annabeth gritted her teeth. She couldn't break down, not when they still had a mission. "Alright, I don't know what's going on with you, but you'd better get your head on straight before we face Erebus."

"It's too late," he muttered menacingly. Completely ignoring them, he took off into the tunnel. Exchanging a helpless glance, they followed him.

They found Percy standing in a dim cavern. A few feet away, a god sat on an obsidian throne. He had pale skin, black windswept hair, and dark eyes. Surprisingly, he was dressed rather casually, with jeans and a leather jacket, and he took the appearance of a young man. Erebus observed them with indifference, but something next to him caught Annabeth's attention.

Slouched in a sitting position, Nico seemed to be sleeping peacefully.

"Aether sent you," Erebus stated. His voice seemed to make the chamber even bleaker. He glared at Percy. "This one is lost to him."

Thalia asked in alarm, "What do you mean?"

Before he could answer, Percy silently took out a metal sword and rushed at him. Annabeth stared in horror, both at what he was doing and the identity of the sword. It was the same one that the boy had used to attack her before!

Panic overwhelmed her. Was he crazy? "Percy, stop!"

Actually listening to her, he froze. He turned toward her, and she gulped. So many thoughts and suspicions about what had happened were turning in her head, and Percy had the overall look of someone who was…possessed. Or maybe sleepwalking was another term.

"You defend him after what he did?" Percy said in a monotone. "You are proving to be a threat." With that, he changed targets and charged at her.