“I was not including thee, boy,” Zoë said. “You are not part of this quest.”

“Hey, I’m trying to save your lives!”

“You shouldn’t have come, Percy,” Thalia said grimly. “But you’re here now. Come on. Let’s get back to the van.”

“That is not thy decision!” Zoë snapped.

Thalia scowled at her. “You’re not the boss here, Zoë. I don’t care how old you are! You’re still a conceited little brat!”

“You never had any wisdom when it came to boys,” Zoë growled. “You never could leave them behind!”

Thalia looked like she was about to hit Zoë. Then everyone froze. I heard a growl so loud I thought one of the rocket engines was starting up.

Below us, a few adults screamed. A little kid’s voice screeched with delight: “Kitty!”

Something enormous bounded up the ramp. It was the size of a pick-up truck, with silver claws and golden glittering fur. I’d seen this monster once before. Two years ago, I’d glimpsed it briefly from a train. Now, up close and personal, it looked even bigger.

“The Nemean Lion,” Thalia said. “Don’t move.”

The lion roared so loud it parted my hair. Its fangs gleamed like stainless steel.

“Separate on my mark,” Zoë said. “Try to keep it distracted.”

“Until when?” Grover asked.

“Until I think of a way to kill it. Go!”

I uncapped Riptide and rolled to the left. Arrows whistled past me, and Grover played a sharp tweet-tweet cadence on his reed pipes. I turned and saw Zoë and Bianca climbing the Apollo capsule. They were firing arrows, one after another, all shattering harmlessly against the lion’s metallic fur. The lion swiped the capsule and tipped it on its side, spilling the Hunters off the back. Grover played a frantic, horrible tune, and the lion turned toward him, but Thalia stepped into its path, holding up Aegis, and the lion recoiled. “ROOOAAAR!”

“Hi-yah!” Thalia said. “Back!”

The lion growled and clawed the air, but it retreated as if the shield were a blazing fire.

For a second, I thought Thalia had it under control. Then I saw the lion crouching, its leg muscles tensing. I’d seen enough cat fights in the alleys around my apartment in New York. I knew the lion was going to pounce.

“Hey!” I yelled. I don’t know what I was thinking, but I charged the beast. I just wanted to get it away from my friends. I slashed with Riptide, a good strike to the flank that should’ve cut the monster into Meow Mix, but the blade just clanged against its fur in a burst of sparks.

The lion raked me with its claws, ripping off a chunk of my coat. I backed against the railing. It sprang at me, one thousand pounds of monster, and I had no choice but to turn and jump.

I landed on the wing of an old-fashioned silver airplane, which pitched and almost spilled me to the floor, three stories below.

An arrow whizzed past my head. The lion jumped onto the aircraft, and the cords holding the plane began to groan.

The lion swiped at me, and I dropped onto the next exhibit, a weird-looking spacecraft with blades like a helicopter. I looked up and saw the lion roar—inside its maw, a pink tongue and throat.

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.

“Zoë!” 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.

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

“No clear shot!” Zoë 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!” Zoë 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.

Zoë 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.

“Zoë, 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. Zoë and Bianca dropped from the balcony and landed next to me.

Zoë eyed me cautiously. “That was . . . an interesting strategy.”

“Hey, it worked.”

She didn’t argue.