"Hey, Big Fella," I called up. "I bet they don't play with you much."

"GROWWWLLLL!"

"Good boy," I said weakly.

I waved the stick. The dog's middle head followed the movement. The other two heads trained their eyes on me, completely ignoring the spirits. I had Cerberus's undivided attention. I wasn't sure that was a good thing.

"Fetch!" I threw the stick into the gloom, a good solid throw. I heard it go ker-sploosh in the River Styx.

Cerberus glared at me, unimpressed. His eyes were baleful and cold.

So much for the plan.

Cerberus was now making a new kind of growl, deeper down in his three throats.

"Um," Grover said. "Percy?"

"Yeah?"

"I just thought you'd want to know."

"Yeah?"

"Cerberus? He's saying we've got ten seconds to pray to the god of our choice. After that… well… he's hungry."

"Wait!" Annabeth said. She started rifling through her pack.

Uh-oh, I thought.

"Five seconds," Grover said. "Do we run now?"

Annabeth produced a red rubber ball the size of a grapefruit. It was labeled WATERLAND, DENVER, CO. Before I could stop her, she raised the ball and marched straight up to Cerberus.

She shouted, "See the ball? You want the ball, Cerberus? Sit!"

Cerberus looked as stunned as we were.

All three of his heads cocked sideways. Six nostrils dilated.

"Sit!" Annabeth called again.

I was sure that any moment she would become the world's largest Milkbone dog biscuit.

But instead, Cerberus licked his three sets of lips, shifted on his haunches, and sat, immediately crushing a dozen spirits who'd been passing underneath him in the EZ DEATH line. The spirits made muffled hisses as they dissipated, like the air let out of tires.

Annabeth said, "Good boy!"

She threw Cerberus the ball.

He caught it in his middle mouth. It was barely big enough for him to chew, and the other heads started snapping at the middle, trying to get the new toy.

"Drop it. " Annabeth ordered.

Cerberus's heads stopped fighting and looked at her. The ball was wedged between two of his teeth like a tiny piece of gum. He made a loud, scary whimper, then dropped the ball, now slimy and bitten nearly in half, at Annabeth's feet.

"Good boy." She picked up the ball, ignoring the monster spit all over it.

She turned toward us. "Go now. EZ DEATH line—it's faster."

I said, "But—"

"Now. " She ordered, in the same tone she was using on the dog.

Grover and I inched forward warily.

Cerberus started to growl.

"Stay!" Annabeth ordered the monster. "If you want the ball, stay!"

Cerberus whimpered, but he stayed where he was.

"What about you?" I asked Annabeth as we passed her.

"I know what I'm doing, Percy," she muttered. "At least, I'm pretty sure…"

Grover and I walked between the monster's legs.

Please, Annabeth, I prayed. Don't tell him to sit again.

We made it through. Cerberus wasn't any less scary-looking from the back.

Annabeth said, "Good dog!"

She held up the tattered red ball, and probably came to the same conclusion I did—if she rewarded Cerberus, there'd be nothing left for another trick.

She threw the ball anyway. The monster's left mouth immediately snatched it up, only to be attacked by the middle head, while the right head moaned in protest.

While the monster was distracted, Annabeth walked briskly under its belly and joined us at the metal detector.

"How did you do that?" I asked her, amazed.

"Obedience school," she said breathlessly, and I was surprised to see there were tears in her eyes. "When I was little, at my dad's house, we had a Doberman…"

"Never mind that," Grover said, tugging at my shirt. "Come on!"

We were about to bolt through the EZ DEATH line when Cerberus moaned pitifully from all three mouths. Annabeth stopped.

She turned to face the dog, which had done a one-eighty to look at us.

Cerberus panted expectantly, the tiny red ball in pieces in a puddle of drool at its feet.

"Good boy," Annabeth said, but her voice sounded melancholy and uncertain.

The monster's heads turned sideways, as if worried about her.

"I'll bring you another ball soon," Annabeth promised faintly. "Would you like that?"

The monster whimpered. I didn't need to speak dog to know Cerberus was still waiting for the ball.

"Good dog. I'll come visit you soon. I–I promise." Annabeth turned to us. "Let's go."

Grover and I pushed through the metal detector, which immediately screamed and set off flashing red lights. "Unauthorized possessions! Magic detected!"

Cerberus started to bark.

We burst through the EZ DEATH gate, which started even more alarms blaring, and raced into the Underworld.

A few minutes later, we were hiding, out of breath, in the rotten trunk of an immense black tree as security ghouls scuttled past, yelling for backup from the Furies.

Grover murmured, "Well, Percy, what have we learned today?"

"That three-headed dogs prefer red rubber balls over sticks?"

"No," Grover told me. "We've learned that your plans really, really bite!"

I wasn't sure about that. I thought maybe Annabeth and I had both had the right idea. Even here in the Underworld, everybody—even monsters—needed a little attention once in a while.

I thought about that as we waited for the ghouls to pass. I pretended not to see Annabeth wipe a tear from her cheek as she listened to the mournful keening of Cerberus in the distance, longing for his new friend.

Imagine the largest concert crowd you've ever seen, a football field packed with a million fans.

Now imagine a field a million times that big, packed with people, and imagine the electricity has gone out, and there is no noise, no light, no beach ball bouncing around over the crowd. Something tragic has happened backstage. Whispering masses of people are just milling around in the shadows, waiting for a concert that will never start.

If you can picture that, you have a pretty good idea what the Fields of Asphodel looked like. The black grass had been trampled by eons of dead feet. A warm, moist wind blew like the breath of a swamp. Black trees—Grover told me they were poplars—grew in clumps here and there.

The cavern ceiling was so high above us it might've been a bank of storm clouds, except for the stalactites, which glowed faint gray and looked wickedly pointed. I tried not to imagine they'd fall on us at any moment, but dotted around the fields were several that had fallen and impaled themselves in the black grass. I guess the dead didn't have to worry about little hazards like being speared by stalactites the size of booster rockets.

Annabeth, Grover, and I tried to blend into the crowd, keeping an eye out for security ghouls. I couldn't help looking for familiar faces among the spirits of Asphodel, but the dead are hard to look at. Their faces shimmer. They all look slightly angry or confused. They will come up to you and speak, but their voices sound like chatter, like bats twittering. Once they realize you can't understand them, they frown and move away.

The dead aren't scary. They're just sad.

We crept along, following the line of new arrivals that snaked from the main gates toward a black-tented pavilion with a banner that read:

JUDGMENTS FOR ELYSIUM AND ETERNAL DAMNATION

Welcome, Newly Deceased!

Out the back of the tent came two much smaller lines.

To the left, spirits flanked by security ghouls were marched down a rocky path toward the Fields of Punishment, which glowed and smoked in the distance, a vast, cracked wasteland with rivers of lava and minefields and miles of barbed wire separating the different torture areas. Even from far away, I could see people being chased by hellhounds, burned at the stake, forced to run naked through cactus patches or listen to opera music. I could just make out a tiny hill, with the ant-size figure of Sisyphus struggling to move his boulder to the top. And I saw worse tortures, too—things I don't want to describe.