"Well?" she demanded.

"Ma'am, I don't…"

"Your time is up," she hissed.

Then the weirdest thing happened. Her eyes began to glow like barbecue coals. Her fingers stretched, turning into talons. Her jacket melted into large, leathery wings. She wasn't human. She was a shriveled hag with bat wings and claws and a mouth full of yellow fangs, and she was about to slice me to ribbons.

Then things got even stranger.

Mr. Brunner, who'd been out in front of the museum a minute before, wheeled his chair into the doorway of the gallery, holding a pen in his hand.

"What ho, Percy!" he shouted, and tossed the pen through the air.

Mrs. Dodds lunged at me.

With a yelp, I dodged and felt talons slash the air next to my ear. I snatched the ballpoint pen out of the air, but when it hit my hand, it wasn't a pen anymore. It was a sword—Mr. Brunner's bronze sword, which he always used on tournament day.

Mrs. Dodds spun toward me with a murderous look in her eyes.

My knees were jelly. My hands were shaking so bad I almost dropped the sword.

She snarled, "Die, honey!"

And she flew straight at me.

Absolute terror ran through my body. I did the only thing that came naturally: I swung the sword.

The metal blade hit her shoulder and passed clean through her body as if she were made of water. Hisss!

Mrs. Dodds was a sand castle in a power fan. She exploded into yellow powder, vaporized on the spot, leaving nothing but the smell of sulfur and a dying screech and a chill of evil in the air, as if those two glowing red eyes were still watching me.

I was alone.

There was a ballpoint pen in my hand.

Mr. Brunner wasn't there. Nobody was there but me.

My hands were still trembling. My lunch must've been contaminated with magic mushrooms or something.

Had I imagined the whole thing?

I went back outside.

It had started to rain.

Grover was sitting by the fountain, a museum map tented over his head. Nancy Bobofit was still standing there, soaked from her swim in the fountain, grumbling to her ugly friends. When she saw me, she said, "I hope Mrs. Kerr whipped your butt."

I said, "Who?"

"Our teacher. Duh!"

I blinked. We had no teacher named Mrs. Kerr. I asked Nancy what she was talking about.

She just rolled her eyes and turned away.

I asked Grover where Mrs. Dodds was.

He said, "Who?"

But he paused first, and he wouldn't look at me, so I thought he was messing with me.

"Not funny, man," I told him. "This is serious."

Thunder boomed overhead.

I saw Mr. Brunner sitting under his red umbrella, reading his book, as if he'd never moved.

I went over to him.

He looked up, a little distracted. "Ah, that would be my pen. Please bring your own writing utensil in the future, Mr. Jackson."

I handed Mr. Brunner his pen. I hadn't even realized I was still holding it.

"Sir," I said, "where's Mrs. Dodds?"

He stared at me blankly. "Who?"

"The other chaperone. Mrs. Dodds. The pre-algebra teacher."

He frowned and sat forward, looking mildly concerned. "Percy, there is no Mrs. Dodds on this trip. As far as I know, there has never been a Mrs. Dodds at Yancy Academy. Are you feeling all right?"

I was used to the occasional weird experience, but usually they were over quickly. This twenty-four/seven hallucination was more than I could handle. For the rest of the school year, the entire campus seemed to be playing some kind of trick on me. The students acted as if they were completely and totally convinced that Mrs. Kerr—a perky blond woman whom I'd never seen in my life until she got on our bus at the end of the field trip—had been our pre-algebra teacher since Christmas.

Every so often I would spring a Mrs. Dodds reference on somebody, just to see if I could trip them up, but they would stare at me like I was psycho.

It got so I almost believed them—Mrs. Dodds had never existed.

Almost.

But Grover couldn't fool me. When I mentioned the name Dodds to him, he would hesitate, then claim she didn't exist. But I knew he was lying.

Something was going on. Something had happened at the museum.

I didn't have much time to think about it during the days, but at night, visions of Mrs. Dodds with talons and leathery wings would wake me up in a cold sweat.

The freak weather continued, which didn't help my mood. One night, a thunderstorm blew out the windows in my dorm room. A few days later, the biggest tornado ever spotted in the Hudson Valley touched down only fifty miles from Yancy Academy. One of the current events we studied in social studies class was the unusual number of small planes that had gone down in sudden squalls in the Atlantic that year.

I started feeling cranky and irritable most of the time. My grades slipped from Ds to Fs. I got into more fights with Nancy Bobofit and her friends. I was sent out into the hallway in almost every class.

Finally, when our English teacher, Mr. Nicoll, asked me for the millionth time why I was too lazy to study for spelling tests, I snapped. I called him an old sot. I wasn't even sure what it meant, but it sounded good.

The headmaster sent my mom a letter the following week, making it official: I would not be invited back next year to Yancy Academy.

Fine, I told myself. Just fine.

I was homesick.

I wanted to be with my mom in our little apartment on the Upper East Side, even if I had to go to public school and put up with my obnoxious stepfather and his stupid poker parties.

And yet… there were things I'd miss at Yancy. The view of the woods out my dorm window, the Hudson River in the distance, the smell of pine trees. I'd miss Grover, who'd been a good friend, even if he was a little strange. I worried how he'd survive next year without me.

I'd miss Latin class, too—Mr. Brunner's crazy tournament days and his faith that I could do well.

As exam week got closer, Latin was the only test I studied for. I hadn't forgotten what Mr. Brunner had told me about this subject being life-and-death for me. I wasn't sure why, but I'd started to believe him.

The evening before my final, I got so frustrated I threw the Cambridge Guide to Greek Mythology across my dorm room. Words had started swimming off the page, circling my head, the letters doing one-eighties as if they were riding skateboards. There was no way I was going to remember the difference between Chiron and Charon, or Polydictes and Polydeuces. And conjugating those Latin verbs? Forget it.

I paced the room, feeling like ants were crawling around inside my shirt.

I remembered Mr. Brunner's serious expression, his thousand-year-old eyes. I will accept only the best from you, Percy Jackson.

I took a deep breath. I picked up the mythology book.

I'd never asked a teacher for help before. Maybe if I talked to Mr. Brunner, he could give me some pointers. At least I could apologize for the big fat F I was about to score on his exam. I didn't want to leave Yancy Academy with him thinking I hadn't tried.

I walked downstairs to the faculty offices. Most of them were dark and empty, but Mr. Brunner's door was ajar, light from his window stretching across the hallway floor.

I was three steps from the door handle when I heard voices inside the office. Mr. Brunner asked a question. A voice that was definitely Grover's said "… worried about Percy, sir."

I froze.

I'm not usually an eavesdropper, but I dare you to try not listening if you hear your best friend talking about you to an adult.

I inched closer.

"… alone this summer," Grover was saying. "I mean, a Kindly One in the school! Now that we know for sure, and they know too—"