Its mouth, I thought. Its fur was completely invulnerable, but if I could strike it in the mouth… The only problem was, the monster moved too quickly. Between its claws and fangs, I couldn't get close without getting sliced to pieces.

"Zoe!" I shouted. "Target the mouth!"

The monster lunged. An arrow zipped past it, missing completely, and I dropped from the spaceship onto the top of a floor exhibit, a huge model of the earth. I slid down Russia and dropped off the equator.

The Nemean Lion growled and steadied itself on the spacecraft, but its weight was too much. One of the cords snapped. As the display swung down like a pendulum, the lion leaped off onto the model earth's North Pole.

"Grover!" I yelled. "Clear the area!"

Groups of kids were running around screaming. Grover tried to corral them away from the monster just as the other cord on the spaceship snapped and the exhibit crashed to the floor. Thalia dropped off the second-floor railing and landed across from me, on the other side of the globe. The lion regarded us both, trying to decide which of us to kill first.

Zoe and Bianca were above us, bows ready, but they kept having to move around to get a good angle.

"No clear shot!" Zoe yelled. "Get it to open its mouth more!"

The lion snarled from the top of the globe.

I looked around. Options. I needed…

The gift shop. I had a vague memory from my trip here as a little kid. Something I'd made my mom buy me, and I'd regretted it. If they still sold that stuff…

"Thalia," I said, "keep it occupied."

She nodded grimly.

"Hi-yah!" She pointed her spear and a spidery arc of blue electricity shot out, zapping the lion in the tail.

"ROOOOOOOAR!" The lion turned and pounced. Thalia rolled out of its way, holding up Aegis to keep the monster at bay, and I ran for the gift shop.

"This is no time for souvenirs, boy!" Zoe yelled.

I dashed into the shop, knocking over rows of T-shirts, jumping over tables full of glow-in-the-dark planets and space ooze. The sales lady didn't protest. She was too busy cowering behind her cash register.

There! On the far wall—glittery silver packets. Whole racks of them. I scooped up every kind I could find and ran out of the shop with an armful.

Zoe and Bianca were still showering arrows on the monster, but it was no good. The lion seemed to know better than to open its mouth too much. It snapped at Thalia, slashing with its claws. It even kept its eyes narrowed to tiny slits.

Thalia jabbed at the monster and backed up. The lion pressed her.

"Percy," she called, "whatever you're going to do—"

The lion roared and swatted her like a cat toy, sending her flying into the side of a Titan rocket. Her head hit the metal and she slid to the floor.

"Hey!" I yelled at the lion. I was too far away to strike, so I took a risk: I hurled Riptide like a throwing knife. It bounced off the lion's side, but that was enough to get the monster's attention. It turned toward me and snarled.

There was only one way to get close enough. I charged, and as the lion leaped to intercept me, I chunked a space food pouch into its maw—a chunk of cellophane-wrapped, freeze-dried strawberry parfait.

The lion's eyes got wide and it gagged like a cat with a hairball.

I couldn't blame it. I remembered feeling the same way when I'd tried to eat space food as a kid. The stuff was just plain nasty.

"Zoe, get ready!" I yelled.

Behind me, I could hear people screaming. Grover was playing another horrible song on his pipes.

I scrambled away from the lion. It managed to choke down the space food packet and looked at me with pure hate.

"Snack time!" I yelled.

It made the mistake of roaring at me, and I got an ice-cream sandwich in its throat. Fortunately, I had always been a pretty good pitcher, even though baseball wasn't my game. Before the lion could stop gagging, I shot in two more flavors of ice cream and a freeze-dried spaghetti dinner.

The lion's eyes bugged. It opened its mouth wide and reared up on its back paws, trying to get away from me.

"Now!" I yelled.

Immediately, arrows pierced the lion's maw—two, four, six. The lion thrashed wildly, turned, and fell backward. And then it was still.

Alarms wailed throughout the museum. People were flocking to the exits. Security guards were running around in a panic with no idea what was going on.

Grover knelt at Thalia's side and helped her up. She seemed okay, just a little dazed. Zoe and Bianca dropped from the balcony and landed next to me.

Zoe eyed me cautiously. "That was… an interesting strategy."

"Hey, it worked."

She didn't argue.

The lion seemed to be melting, the way dead monsters do sometimes, until there was nothing left but its glittering fur coat, and even that seemed to be shrinking to the size of a normal lion's pelt.

"Take it," Zoe told me.

I stared at her. "What, the lion's fur? Isn't that, like, an animal rights violation or something?"

"It is a spoil of war," she told me. "It is rightly thine."

"You killed it," I said.

She shook her head, almost smiling. "I think thy ice-cream sandwich did that. Fair is fair, Percy Jackson. Take the fur."

I lifted it up; it was surprisingly light. The fur was smooth and soft. It didn't feel at all like something that could stop a blade. As I watched, the pelt shifted and changed into a coat—a full-length golden-brown duster.

"Not exactly my style," I murmured.

"We have to get out of here," Grover said. "The security guards won't stay confused for long."

I noticed for the first time how strange it was that the guards hadn't rushed forward to arrest us. They were scrambling in all directions except ours, like they were madly searching for something. A few were running into the walls or each other.

"You did that?" I asked Grover.

He nodded, looking a little embarrassed. "A minor confusion song. I played some Barry Manilow. It works every time. But it'll only last a few seconds."

"The security guards are not our biggest worry," Zoe said. "Look."

Through the glass walls of the museum, I could see a group of men walking across the lawn. Gray men in gray camouflage outfits. They were too far away for us to see their eyes, but I could feel their gaze aimed straight at me.

"Go," I said. "They'll be hunting me. I'll distract them."

"No," Zoe said. "We go together."

I stared at her. "But, you said—"

"You are part of this quest now," Zoe said grudgingly. "I do not like it, but there is no changing fate. You are the fifth quest member. And we are not leaving anyone behind."

We were crossing the Potomac when we spotted the helicopter. It was a sleek, black military model just like the one we'd seen at Westover Hall. And it was coming straight toward us.

"They know the van," I said. "We have to ditch it."

Zoe swerved into the fast lane. The helicopter was gaining.

"Maybe the military will shoot it down," Grover said hopefully.

"The military probably thinks it's one of theirs," I said. "How can the General use mortals, anyway?"

"Mercenaries," Zoe said bitterly. "It is distasteful, but many mortals will fight for any cause as long as they are paid."

"But don't these mortals see who they're working for?" I asked. "Don't they notice all the monsters around them?"

Zoe shook her head. "I do not know how much they see through the Mist. I doubt it would matter to them if they knew the truth. Sometimes mortals can be more horrible than monsters."

The helicopter kept coming, making a lot better time than we were through D.C. traffic.

Thalia closed her eyes and prayed hard. "Hey, Dad. A lightning bolt would be nice about now. Please?"