THEY WERE DOING OKAY UNTIL THEY HIT THE TREE ROOTS. The spider raced along and they were keeping up, but then they spotted a tunnel off to the side that was dug from raw earth, and wrapped in thick roots. Grover stopped dead in his tracks.

"What is it?" Percy asked.

He didn't move. He stared openmouthed into the dark tunnel. His curly hair rustled in the breeze.

"Come on!" Annabeth urged, "We have to keep moving."

"This is the way," Grover muttered in awe. "This is it."

"What way?" Percy asked. 

"It's the way to Pan, isn't it?" Selena questioned, "You sense him?"

Grover looked at Tyson. "Don't you smell it?"

"Dirt," Tyson said. "And plants."

"Yes! This is the way. I'm sure of it!" Up ahead, the spider was getting farther down the stone corridor. A few more seconds and they'd lose it.

"Well come back," Annabeth promised. "On our way back to Hephaestus."

"The tunnel will be gone by then," Grover said. "I have to follow it. A door like this won't stay open!"

"But we can't," Annabeth said. "The forges!"

Grover looked at her sadly. "I have to, Annabeth. Don't you understand?"

"Annie, that was part of the reason to come down here in the first place, remember?" Selena stated,

Annabeth looked desperate, like she didn't understand at all. The spider was almost out of sight.

"We'll split up," Percy stated,

"No!" Annabeth said. "That's way too dangerous. How will we ever find each other again? And Grover can't go alone."

Tyson put his hand on Grover's shoulder. "I—I will go with him."

Selena couldn't believe she was hearing this. "Tyson, are you sure?" Percy asked,

The big guy nodded. "Goat boy needs help. We will find the God person. I am not like Hephaestus. I trust friends."

Grover took a deep breath. "Percy, we'll find each other again. We've still got the empathy link. I just...have to."

Selena didn't blame him. This was his life's goal. If he didn't find Pan on this journey, the council would never give him another chance.

"I hope you're right," Percy said.

"I know I am." Selena had never heard him sound so confident about anything, except maybe that cheese enchiladas were better than chicken enchiladas.

"Be careful," Percy told him. Then he looked at Tyson. He gulped back a sob and gave Percy a hug that just about squeezed his eyes out of their sockets. Then he and Grover disappeared through the tunnel of tree roots and were lost in the darkness.

"This is bad," Annabeth said. "Splitting up is a really, really bad idea."

"We'll see them again," Selena said, trying to sound confident. "Now come on. The spider is getting away!"

It wasn't long before the tunnel started to get hot.

The stone walls glowed. The air felt as if they were walking through an oven. The tunnel sloped down and Selena could hear a loud roar, like a river of metal. The spider skittered along, with Annabeth right behind.

"Hey, wait up," Percy called to her.

She glanced back at them. "Yeah?"

"Something Hephaestus said back there...about Athena."

"She swore never to marry," Annabeth said. "Like Artemis and Hestia. She's one of the maiden goddesses."

Percy blinked. "But then—"

"How come she has demigod children?"

Percy nodded, his cheeks pink.

"Percy, you know how Athena was born?"

"She sprung from the head of Zeus in full battle armor or something." He answered,

"Exactly. She wasn't born in the normal way. She was literally born from thoughts. Her children are born the same way. When Athena falls in love with a mortal man, it's purely intellectual, the way she loved Odysseus in the old stories. It's a meeting of minds. She would tell you that's the purest kind of love."

"So your dad and Athena...so you weren't..."

"I was a brain child," Annabeth said. "Literally. Children of Athena are sprung from the divine thoughts of our mother and the mortal ingenuity of our father. We are supposed to be a gift, a blessing from Athena on the men she favors."

"But—"

"Percy, the spider's getting away. Do you really want me to explain the exact details of how I was born?"

"Um...no. That's okay."

She smirked. "I thought not." And she ran ahead. Selena snickered at Percy before she followed her blonde friend. 

The roaring got louder. After another half mile or so, they emerged in a cavern the size of a Super Bowl stadium. Their spider escort stopped and curled into a ball. They had arrived at the forge of Hephaestus.

There was no floor, just bubbling lava hundreds of feet below. They stood on a rock ridge that circled the cavern. A network of metal bridges spanned across it. At the center was a huge platform with all sorts of machines, cauldrons, forges, and the largest anvil Selena had ever seen—a block of iron the size of a house. Creatures moved around the platform—several strange, dark shapes, but they were too far away to make out details.

Annabeth picked up the metal spider and slipped it into her pocket. "I can. Wait here."

"Annie, maybe I should go." Selena offered,

"It's fine. I got it." Annabeth said before she put on her Yankees cap and turned invisible.

Selena sighed, "She shouldn't go off on her own."

Percy and Selena crept along the outer rim of the lava lake, hoping they could get a better angle to see what was happening in the middle.

The heat was horrible. Geryon's ranch had been a winter wonderland compared to this. In no time they were drenched with sweat. Selena's eyes stung from the smoke. They moved along, trying to keep away from the edge, until Percy and Selena found their way blocked by a cart on metal wheels, like the kind they use in mine shafts. Percy lifted up the tarp and found it was half full of scrap metal. They were about to squeeze their way around it when they heard voices from up ahead, probably from a side tunnel.

"Bring it in?" one asked.

"Yeah," another said. "Movie's just about done."

They panicked. Percy and Selena didn't have time to back up. There was nowhere to hide except...the cart. Percy helped her inside before jumping in and pulled the tarp over themselves, hoping no one had seen them. Selena wrapped one hand around Percy's and put her other one around the hilt of her dagger in case the needed to fight. Percy had the same idea as he held onto Riptide.

The cart lurched forward.

"Oi," a gruff voice said. "Thing weighs a ton."

"It's celestial bronze," the other said. "What did you expect?"

They got pulled along. They turned a corner, and from the sound of the wheels echoing against the walls Selena guessed they had passed down a tunnel and into a smaller room. Hopefully they were not about to be dumped into a smelting pot. If they started to tip them over, they'd have to fight their way out quick. 

Selena heard lots of talking, chattering voices that didn't sound human—somewhere between a seal's bark and a dog's growl. There were other sounds too—like an old-fashioned film projector and a tinny voice narrating.

"Just set it in the back," a new voice ordered from across the room. "Now, younglings, please attend to the film. There will be time for questions afterward."

The voices quieted down, and Selena could hear the film.

"As a young sea demon matures," the narrator said, "changes happen in the monster's body. You may notice your fangs getting longer and you may have a sudden desire to devour human beings. These changes are perfectly normal and happen to all young monsters."

Excited snarling filled the room. The teacher told the younglings to be quiet, and the film continued. Selena didn't understand most of it, and she didn't dare look. The film kept talking about growth spurts and acne problems caused by working in the forges, and proper flipper hygiene, and finally it was over.

"Now, younglings," the instructor said, "what is the proper name of our kind?"

"Sea demons!" one of them barked.

"No. Anyone else?"

"Telekhines!" another monster growled.

"Very good," the instructor said. "And why are we here?"

"Revenge!" several shouted.

"Yes, yes, but why?"

"Zeus is evil!" one monster said. "He cast us into Tartarus just because we used magic!"

"Indeed," the instructor said. "After we made so many of the Gods' finest weapons. The trident of Poseidon, for one. And of course—we made the greatest weapon of the Titans! Nevertheless, Zeus cast us away and relied on those fumbling Cyclopes. That is why we are taking over the forges of the usurper Hephaestus. And soon we will control the undersea furnaces, our ancestral home!"

"And so, younglings," the instructor continued, "who do we serve?"

"Kronos!" they shouted.

"And when you grow to be big telekhines, will you make weapons for the army?"

"Yes!"

"Excellent. Now, we've brought in some scraps for you to practice with. Let's see how ingenious you are."

There was a rush of movement and excited voices coming toward the cart. Selena got ready to attack. The tarp was thrown back. Percy and Selena jumped up, Percy prepared to use his sword while Selena took out her dagger and found themselves facing a bunch of...dogs.

Well, their faces were dogs, anyway, with black snouts, brown eyes, and pointy ears. Their bodies were sleek and black like sea mammals, with stubby legs that were half flipper, half foot, and humanlike hands with sharp claws. If you blended together a kid, a Doberman pinscher, and a sea lion, you'd get something like what they were looking at.

"A demigod!" one snarled.

"Eat it!" yelled another.

But that's as far as they got before Percy slashed a wide arc with Riptide and vaporized the entire front row of monsters.

"Back off!" He yelled at the rest, trying to sound fierce. Behind them stood their instructor—a six-foot-tall telekhine with Doberman fangs snarling at them. Percy did his best to stare him down.

"New lesson, class," Selena announced, green mist surrounding her hands as her eyes turned green once again and the bronze in the cart raised up, "Most monsters will vaporize when sliced with a celestial bronze sword. This change is perfectly normal, and will happen to you right now if you don't BACK OFF!"

To their surprise, it worked. The monsters backed up, but there were at least twenty of them. Her fear factor wasn't going to last long.

Percy jumped out of the cart, yelled, "CLASS DISMISSED!" Selena followed him, the brozne falling to the ground and they ran for the exit.

The monsters charged after them, barking and growling. She hoped they couldn't run very fast with those stubby little legs and flippers, but they waddled along pretty well. Thank the Gods there was a door in the tunnel leading out to the main cavern. Percy slammed it shut and Selena turned the wheel handle to lock it, but they doubted it would keep them long.

She didn't know what to do. Annabeth was out here somewhere, invisible. Their chance for a subtle reconnaissance mission had been blown. Percy and Selena ran toward the platform at the center of the lava lake.