I wasn't liking Mr. D much, but there was something about the way he called me mortal, as if… he wasn't. It was enough to put a lump in my throat, to suggest why Grover was dutifully minding his cards, chewing his soda can, and keeping his mouth shut.

"Percy," Chiron said, "you may choose to believe or not, but the fact is that immortal means immortal. Can you imagine that for a moment, never dying? Never fading? Existing, just as you are, for all time?"

I was about to answer, off the top of my head, that it sounded like a pretty good deal, but the tone of Chiron's voice made me hesitate.

"You mean, whether people believed in you or not," I said.

"Exactly," Chiron agreed. "If you were a god, how would you like being called a myth, an old story to explain lightning? What if I told you, Perseus Jackson, that someday people would call you a myth, just created to explain how little boys can get over losing their mothers?"

My heart pounded. He was trying to make me angry for some reason, but I wasn't going to let him. I said, "I wouldn't like it. But I don't believe in gods."

"Oh, you'd better," Mr. D murmured. "Before one of them incinerates you."

Grover said, "P-please, sir. He's just lost his mother. He's in shock."

"A lucky thing, too," Mr. D grumbled, playing a card. "Bad enough I'm confined to this miserable job, working with boys who don't even believe. "

He waved his hand and a goblet appeared on the table, as if the sunlight had bent, momentarily, and woven the air into glass. The goblet filled itself with red wine.

My jaw dropped, but Chiron hardly looked up.

"Mr. D," he warned, "your restrictions."

Mr. D looked at the wine and feigned surprise.

"Dear me." He looked at the sky and yelled, "Old habits! Sorry!"

More thunder.

Mr. D waved his hand again, and the wineglass changed into a fresh can of Diet Coke. He sighed unhappily, popped the top of the soda, and went back to his card game.

Chiron winked at me. "Mr. D offended his father a while back, took a fancy to a wood nymph who had been declared off-limits."

"A wood nymph," I repeated, still staring at the Diet Coke can like it was from outer space.

"Yes," Mr. D confessed. "Father loves to punish me. The first time, Prohibition. Ghastly! Absolutely horrid ten years! The second time—well, she really was pretty, and I couldn't stay away—the second time, he sent me here. Half-Blood Hill. Summer camp for brats like you. 'Be a better influence, he told me. 'Work with youths rather than tearing them down. Ha. Absolutely unfair."

Mr. D sounded about six years old, like a pouting little kid.

"And…" I stammered, "your father is…"

"Di immortales, Chiron," Mr. D said. "I thought you taught this boy the basics. My father is Zeus, of course."

I ran through D names from Greek mythology. Wine. The skin of a tiger. The satyrs that all seemed to work here. The way Grover cringed, as if Mr. D were his master.

"You're Dionysus," I said. "The god of wine."

Mr. D rolled his eyes. "What do they say, these days, Grover? Do the children say, 'Well, duh! ?"

"Y-yes, Mr. D."

"Then, well, duh! Percy Jackson. Did you think I was Aphrodite, perhaps?"

"You're a god."

"Yes, child."

"A god. You."

He turned to look at me straight on, and I saw a kind of purplish fire in his eyes, a hint that this whiny, plump little man was only showing me the tiniest bit of his true nature. I saw visions of grape vines choking unbelievers to death, drunken warriors insane with battle lust, sailors screaming as their hands turned to flippers, their faces elongating into dolphin snouts. I knew that if I pushed him, Mr. D would show me worse things. He would plant a disease in my brain that would leave me wearing a strait-jacket in a rubber room for the rest of my life.

"Would you like to test me, child?" he said quietly.

"No. No, sir."

The fire died a little. He turned back to his card game. "I believe I win."

"Not quite, Mr. D," Chiron said. He set down a straight, tallied the points, and said, "The game goes to me."

I thought Mr. D was going to vaporize Chiron right out of his wheelchair, but he just sighed through his nose, as if he were used to being beaten by the Latin teacher. He got up, and Grover rose, too.

"I'm tired," Mr. D said. "I believe I'll take a nap before the sing-along tonight. But first, Grover, we need to talk, again, about your less-than-perfect performance on this assignment."

Grover's face beaded with sweat. "Y-yes, sir."

Mr. D turned to me. "Cabin eleven, Percy Jackson. And mind your manners."

He swept into the farmhouse, Grover following miserably.

"Will Grover be okay?" I asked Chiron.

Chiron nodded, though he looked a bit troubled. "Old Dionysus isn't really mad. He just hates his job. He's been… ah, grounded, I guess you would say, and he can't stand waiting another century before he's allowed to go back to Olympus."

"Mount Olympus," I said. "You're telling me there really is a palace there?"

"Well now, there's Mount Olympus in Greece. And then there's the home of the gods, the convergence point of their powers, which did indeed used to be on Mount Olympus. It's still called Mount Olympus, out of respect to the old ways, but the palace moves, Percy, just as the gods do."

"You mean the Greek gods are here? Like… in America?"

"Well, certainly. The gods move with the heart of the West."

"The what?"

"Come now, Percy. What you call 'Western civilization. Do you think it's just an abstract concept? No, it's a living force. A collective consciousness that has burned bright for thousands of years. The gods are part of it. You might even say they are the source of it, or at least, they are tied so tightly to it that they couldn't possibly fade, not unless all of Western civilization were obliterated. The fire started in Greece. Then, as you well know—or as I hope you know, since you passed my course—the heart of the fire moved to Rome, and so did the gods. Oh, different names, perhaps—Jupiter for Zeus, Venus for Aphrodite, and so on—but the same forces, the same gods."

"And then they died."

"Died? No. Did the West die? The gods simply moved, to Germany, to France, to Spain, for a while. Wherever the flame was brightest, the gods were there. They spent several centuries in England. All you need to do is look at the architecture. People do not forget the gods. Every place they've ruled, for the last three thousand years, you can see them in paintings, in statues, on the most important buildings. And yes, Percy, of course they are now in your United States. Look at your symbol, the eagle of Zeus. Look at the statue of Prometheus in Rockefeller Center, the Greek facades of your government buildings in Washington. I defy you to find any American city where the Olympians are not prominently displayed in multiple places. Like it or not—and believe me, plenty of people weren't very fond of Rome, either—America is now the heart of the flame. It is the great power of the West. And so Olympus is here. And we are here."

It was all too much, especially the fact that I seemed to be included in Chiron's we, as if I were part of some club.

"Who are you, Chiron? Who… who am I?"

Chiron smiled. He shifted his weight as if he were going to get up out of his wheelchair, but I knew that was impossible. He was paralyzed from the waist down.

"Who are you?" he mused. "Well, that's the question we all want answered, isn't it? But for now, we should get you a bunk in cabin eleven. There will be new friends to meet. And plenty of time for lessons tomorrow. Besides, there will be s'mores at the campfire tonight, and I simply adore chocolate."

And then he did rise from his wheelchair. But there was something odd about the way he did it. His blanket fell away from his legs, but the legs didn't move. His waist kept getting longer, rising above his belt. At first, I thought he was wearing very long, white velvet underwear, but as he kept rising out of the chair, taller than any man, I realized that the velvet underwear wasn't underwear; it was the front of an animal, muscle and sinew under coarse white fur. And the wheelchair wasn't a chair. It was some kind of container, an enormous box on wheels, and it must've been magic, because there's no way it could've held all of him. A leg came out, long and knobby-kneed, with a huge polished hoof. Then another front leg, then hindquarters, and then the box was empty, nothing but a metal shell with a couple of fake human legs attached.