Nina growled, her skin rearranging itself. She hunkered down and charged Ellie. Nina tackled her and they tumbled, rolling down a small gra.s.sy hill. Mist and stink masked them both.

"Nina?" I could only whisper. What happened? The mama ducked back in the house, clicked the lock shut, and turned off the spotlight, leaving us in the dark.

"Ellie!" Brennan shouted. He threw my elbow aside and charged into the mist. "Ellie?"

I charged in then, too. "Ellie!" My eyes stung from the mist, tears streaming down my cheeks. I couldn't see anything but green-gray, the fog was too thick, the night too dark. I started gagging. I heard Dillon's voice call in, "Hey! You guys okay?"

Then I heard it: Ellie's giggle. In stereo.

"Sure," Ellie said. Twice.

The fog lifted.

Two Ellies.

My heart paused. I squeezed my eyes, opened them again, thinking this a trick of my watery sight. My Nina was now...Ellie? It couldn't be. My heart broke. Nina had been right there.

But no, I was seeing this correctly: two blond ponytails, two torn peace-sign sweatshirts, two messenger bags, two sets of nibbled fingernails.

"What the-?" Brennan choked.

"Whoa," Dillon breathed.

Ellie One turned to Ellie Two. (Or maybe it was Ellie Two who turned to Ellie One?) Then the other Ellie turned as well. The Ellies looked at one another.

And both screamed.

Both started crying.

"Wait, wait, wait," I said. I grabbed each Ellie by the shoulder. Both felt real, both sets of eyes were so human. No trace of my Nina left. No trace. I gripped the Ellies harder, looking from one Ellie to the other, my heart thudding in my ears. Exact mirror images. Identical. Twins.

"Twins," Brennan muttered. "Gemini-the twins."

"But where is our Gemini?" I scanned the area in desperation, hoping for a glimpse of a billowing toga. What was going on? "Is this her?" I remembered the warning Gemini had given back at my house, the warning she'd issued before helping us: I won't be so polite the next time our paths cross. Had she just been tricking us, being nice until now?

"Jalen, it's me! I'm Ellie! I'm her!" one of the Ellies claimed.

"Jalen, no! It's me! She's not-she's..." More tears.

"Jalen, you have to believe me!" Red-faced anger from this Ellie.

"Jalen, don't! It's me! Don't you believe me?"

I swallowed hard. I didn't know which Ellie was my Ellie. Was I supposed to guess? I blinked back tears. If this had happened hours ago, I'd know my Ellie without a doubt. But the new Ellie...could I pick her out for certain?

"Who is your homeroom teacher?" I choked out.

"Mrs. McGill," they answered like a chorus. They turned to each other and grew teary-eyed again.

"What did you dress as for Halloween last year?" Brennan asked.

Both Ellies answered in unison, "A hippie." One Ellie started shaking, the other bit her lip and tried to reel in the tears.

"Whoa," Dillon said again. His wide eyes glowed in the night like a cat's.

The book! Real Ellie had a copy of The Keypers of the Zodiack.

"Let me see the book," I said.

Both Ellies reached into the messenger bag strapped across her chest and retrieved identical copies of The Keypers of the Zodiack. Great. Now there were two copies of this dangerous book. I flipped through both in panic. Identical, as far as I could tell. I turned to the entry on Gemini and read.

"'Gemini, the twins. June 20July 20. Thou art charming times two, Gemini. Thine impulsive, curious nature provides thee with a cache of friends, albeit none too dear-thy cynicism and impatience makes deep relationships rare. Thou couldst not risk another coming between thee and thy twin. But, this same trait allows thee an adaptability unseen in others. Thou art a quick-witted, restless communicator, sometimes breathing life into gatherings, sometimes driving others to madness. Remember, Gemini, that thy duality oft leads to deception. In the end, thou canst not abide suffering, and thou will make great sacrifices to avoid seeing loved ones destruct.'"

By now, one Ellie was sobbing to the point of gagging. The other sat on the curb, holding her head and muttering, "No, no, no!"

Which was Ellie? I shook my head and turned to Brennan.

"Brennan, do you-?"

He trembled. He paced between the two, looking each squarely in the eyes. He trembled more. "No."

More wails from both Ellies this time.

At last, Gemini, our guide, appeared. Dillon scrambled backward in the dirt.

"What is this?" I flung my hand at these two versions of my best friend. "Is this a Gemini twin? Why doesn't she look like you? Where did Nina go?"

Gemini took a shaky breath and stroked her hair. "I warned that you would face all twelve Keepers, and this is your Gemini Challenge, Jalen. The Gemini power is the power to twin anyone in the world, living or dead. You must pick which is your best friend and defeat the other."

"Defeat?" I wailed. I looked at both Ellies, both looking at me with tear-stained faces and red-rimmed, pleading eyes. Gemini's twin-obviously the evil twin-had mimicked Nina to trap me. And now? "What does that mean, defeat?"

"I believe you know what it means," Gemini whispered to the ground. "Consider this. It's better than having to battle your grandmother."

Fire choked me. I growled, balled my fist, and punched the brick house. My knuckles exploded in pain.

Brennan ran at our guide in a tackle stance. "Give me back my sister!" But before he even touched her, he flew backward, like he had bounced off a wall.

"Ah, ah, ah!" our guide said, twitching her finger. Her midnight eyes throbbed, darker than anything else in the night. "Think about your actions. You do not need to anger me."

I grabbed one Ellie's hand, paused, then grabbed the other Ellie's hand, too. One of my hands touched my best friend. The other one touched a predator. Which was which?

"You're both coming."

Running away from that cozy spot was like getting a bucket of ice water dumped over my head. Alarming, awful, but awakening. No Nina, an extra Ellie. We stopped at last to catch our breath.

I was surprised Dillon stuck by us. "You're still here," I said between breaths. He nodded and dropped his tuba, a wheeze sounding under his panting.

"Y'all are obviously in some deep doo-doo," he said, lifting his chin at the pair of Ellies. "I'm not leaving you. It's just getting interesting." He winked at me. Sparks glimmered inside my chest when he did, despite where we were.

The area was industrial, dark, with one solitary barge docked on the river. The river slap-slap-slapped the barge, the bank. A crane on bulldozer wheels hoisted an empty seafood cage above the barge. Tomorrow the crane would lower the huge cage, and the barge would bring it back to the fishing boats in the Gulf. Life moving forward, despite everyone changing. It would, right? Move forward?

"So what's going on here, exactly?" Dillon asked. "If I'm going to help you, I want to know what we're up against." We paused, and then I nodded at Brennan. He started to explain, telling Dillon all about the Keepers of the Zodiac with huge arm gestures and oversize, snarling facial expressions. This was where Dillon would leave us for sure. And probably call the police. And probably a few psychiatrists.

I had to turn away from Brennan's explanation, because I hardly believed it myself. I looked instead from one Ellie to the other. I felt nothing. Nada. Before, I had been excellent at reading people. No, if I'm being honest, let's call it what it was: judging people. But now-nothing. One of the Ellies saw my eyes darting between her and her twin, and a tear slid down her cheek. Wouldn't that be the real Ellie? Could the Keepers be that accurate? And yet I'd seen people transform into beasts just this evening. They'd almost fooled me, trapping me by impersonating my own Nina. Surely an imposter Ellie could whip up a few tears on command. No, I couldn't just guess. The danger of guessing wrong was too great. I had to be certain.

"So then who was that?" Dillon asked.

I startled at his question.

Dillon licked his lips, and it made me realize how thirsty I was. "I mean, not the crazy old lady turning young." He looked at the pair of Ellies. "No offense. I mean that mom?"

Both Ellies dug The Keypers of the Zodiack from a messenger bag, like it was a race to see who could get the answer the fastest. "Cancer!" they both shouted.

They started reading in a blur of words: "'Cancer, the crab. July 21August 9.'"

"Stop!" I snapped. Both Ellie heads shot up. My knee bounced-still no clue which twin was which. I cracked my knuckles. "I can't understand when you both read." I pointed at the closest Ellie.

"You," I said. "Read." The other Ellie slammed her copy of the book closed and kicked the gravel. The closest Ellie gloated and read like the teacher's pet.

"'Cancer, the crab. July 21August 9. Cancer, thou wert sent by King Eurystheus to distract Hercules while he battled the nine-headed Hydra sea monster. That is therefore thy gift: the gift of distraction. Thou preferest to think of it as the gift of hospitality. Though it comes not without a price: One must praise thine efforts in order to gain thine affections. But when thine affections are won, no one is more nurturing or caring than thou art. Thy need for constant love and encouragement contradicts thy lack of trust in others. Contradiction, in fact, is at thy core. Thy moods are shifty and unpredictable, from sullen to smiling to stormy in seconds. Cancer, thou art a feeling being, ruled by the heart. And yet thy memory is long, and when thou feelest wronged, thy need to bury thine opponents overwhelms. Avoid this need, as it may disrupt sought-after security. The pressure thou placest upon thyself is too intense; beware lest thou explode."

"Well, that doesn't paint a pretty picture at all, does it?"

I spun to see Cancer standing there, a jacket thrust out to me. A cigarette ember bounced an inch from her red lips. The irony of the fact that Cancer was a smoker was not lost on me. "Mmm-hmmm," she breathed. "Not pretty at all."

Smoke filtered out of her nostrils. I was reminded of a dragon. A dragon in an ap.r.o.n.

"Jalen," she breathed in a cloud of smoke. "At least, put on this jacket. You look so cold."

Cold. I was cold. Wasn't I?

"No!" I said. I grit my teeth to prevent them from suddenly chattering. I wasn't cold. Why did I want that jacket so badly? "No, not cold."

Cancer lowered the jacket, stomped out her glowing cigarette. The orange fire squashed so quickly beneath her pointy patent-leather toe. "No jacket then. Fine."

Cancer's lipsticked smile stretched as tight as a rubber band across her face, but her eyes were steely knives. The picture of contradiction. Her maternal leanings tugged her in one direction, her fury and power and madness pulled her in the other. Cancer had a hard sh.e.l.l and a mighty pinch.

I longed for that jacket. It looked cozy and warm and soft. It would protect me.

"No jacket," she said, her words etched like ice on air. "Be cold."

"And you," she said, spinning and pointing at one of the Ellies. "I'll show you who's an idiot."

And then, she disintegrated. Cancer dissolved like candle wax, melting into a low pool of smelly mist. The ap.r.o.n strings untied and shriveled into long, pinching claws. The lipstick swelled and spread across her skin, turning every inch of her red. The pearl necklace hardened into a tough outer sh.e.l.l. Cancer doubled into two crabs, then again to four, then again and again and again.

I scurried backward, but Ellie-the one nearby, the one she had called an idiot-stumbled and fell. A tidal wave of slick crabs swelled from the mist, higher and higher and higher, a writhing, crawling wave of crustaceans. It crashed down over a screaming Ellie.

"Ellie!" I yelled too late.

A shrill creak split the air, the sound of rusted metal forced into action. The bulldozer crane behind me whirled about. The seafood cage was no longer empty; it was teeming with hundreds of crusty, snapping crabs.

The hatch on the cage sprang open, and hundreds of crabs rained down on top of the existing pile. It buried Ellie under another wave of crab bodies, crab legs, crab claws.

It was a small mountain of crustaceans, taller and wider than a bus, and it had swallowed one of the Ellies whole. We had to dig her out of there. She wouldn't be able to breathe for long under those pounds and pounds of crabs. But digging through a pile of crabs was like digging through a pile of sharp slabs of rock, plus slime and stink.

Brennan and Dillon had already started flinging clumps of crab bodies aside. I did the same. The other Ellie, the free Ellie, grabbed my elbow.

"Jalen, stop! I'm the real Ellie! Stop digging-you're saving a Keeper!"

I paused and looked into her green eyes. They twinkled-with what? Tears? Amus.e.m.e.nt?

"Jalen, that is Gemini under there. You heard what Cancer said! She's getting even with Gemini for calling her an idiot! Let them duke it out!" Ellie grabbed me by the elbow and started pulling me away. I followed.

But. Wasn't she pulling a little too hard?

Was this Ellie telling the truth? Or was this a Keeper, trying to convince me to stop rescuing my best friend? That would weaken me more than anything else the Keepers could conjure if I was somehow involved in hurting my friends. They'd defeat me for certain if that happened.

"Jalen!" Brennan yelled over the clicking crabs. "Where are you going?"

It could be a trick, couldn't it? Cancer could be tricking me. She would trick me into thinking she was just getting even with Gemini, when it was actually my Ellie under there. Cancer was manipulative. She would do that, wouldn't she? To win?

"Don't you believe me, Jalen?" this Ellie asked. Her voice wavered.

If I didn't dig for the buried Ellie, I was choosing, wasn't I? Which Ellie I thought was mine? I wasn't ready to make that choice.

"I can't," I said. And I didn't have any more time to ponder which Ellie was which. I decided to climb.

But climbing a hill of clicking, shifty crab bodies wasn't easy. Placing my feet and hands on them did relatively nothing; the crabs I touched would simply slide down the mountain of sh.e.l.l to the bottom, tiny landslides every time I tried to gain traction. And crabs are made of everything awful: hard sh.e.l.ls, thick pinchers, slick bodies, heavy stink. The cut on my ear stung like acid from all the crab muck.

My hands would plunge into the swarm and I'd feel a sharp pinch. I'd remove my hand to find a crab clamped onto my finger, and I'd have to sling it aside before starting again. I could only imagine what Ellie was going through in there at the heart of the crab hive. I couldn't even hear if she was screaming; the click-clacking of hundreds of crab legs and pinchers was near deafening. And the other Ellie, the free one, kept begging me, begging Brennan, begging Dillon, to believe that she was our Ellie. It was hard not to believe her.

I finally decided to keep my feet planted on the ground. I started flinging the crabs aside with my hands, like a dog digging a hole. It was faster, yes, but the crabs I launched to either side marched back to their pack like an army of zombies.

I plunged my hand into the ma.s.s again and drew it back sharply-a sliver of crab sh.e.l.l pierced me under my fingernail. I saw white, then orange anger cleared the pain. My anger was sharper than these crabs. I knew this.

That's when I saw Brennan scaling the bulldozer. Free Ellie pleaded with him to get down, begged him to believe her. He ignored her. He stood on top of the six-foot-high treaded wheels, covered his face with his arms, and jumped into the clot.

"Brennan, wait!" I yelled. He disappeared almost immediately. Between seeing that and the overpowering stench of the crabs, I turned my head to the side and retched. The free Ellie sobbed and shouted, "No!" She plunged her hands in at last, covering herself in slime.

Would a Keeper do that? I wondered. Appear so concerned about Brennan? I decided that, yes, she would if she's playing the game right. If I lose the Gemini Challenge by guessing the incorrect Ellie, then she's doing everything in her power to confuse me. I slicked back my hair with my forearm, leaving a trail of gooey crab chunks across my scalp. I kept digging.

Moments later, the other Ellie's head shot out of the center of the fester like she was propelled from below. She gulped in a deep, wheezing breath. Brennan's head popped up next to hers, and then the side of the mountain began to crumble. Brennan had righted Ellie on her feet. They were pushing their way through the crabs.

Dillon grabbed them both and dragged them aside, the crab muck shimmering on them all. Ellie had crabs tangled in her hair and a deep gash on her left cheek. She wasn't screaming, but tears streamed down her face, cleaning away blood and crab guts. Brennan yanked a crab pinched to his ear and howled.

Cancer wasn't done with us yet. The crabs thinned out and scurried around us, turning the ground into a moving, swelling thing.

Brennan stepped on a crab and slipped. When he stood again, a dozen crabs were pinched to his skin. He looked down, and at that moment, I saw his eyes twinkle.