I nodded. It resembled a slightly smaller version of the skeleton in the Great Hall of the House of Wenders, back on the island. As we stepped to the end of a long, snaky ticket line, I craned my neck up to see its head.

I almost missed the man wearing a dark robe, who disappeared into the exhibit hall behind the skeleton.

I jabbed Dad in the side. "Look!"

"Massa?" Dad asked.

"Where?" Cass said.

"You are too hyped up!" Aly said.

"Normal people don't wear robes!" I shouted.

I bolted toward the front of the line, barged past the ticket taker, and raced into the exhibit hall. It was a high-ceilinged room with a balcony, and in the center was a circular display of enormous elephants. The floor on all sides was crowded with families and school groups. I ran to the right, leaping to see over people's heads.

There.

I caught a better glimpse of him now, his robe swinging as he walked. I thought he was heading out the other side, but he seemed to change his mind. Picking up speed, he made a full circle and headed back out the exhibit entrance.

Had he seen me?

"Excuse me . . . sorry . . ." I pushed my way through, nearly trampling a two-year-old in my path, and stumbled into the hallway outside the room.

Elevators lined both walls, but only one car was open-and it was closing, jammed with people. I saw a bearded face, a flash of the robe's material, before the door shut.

A "down" arrow lit up. Behind me was a set of marble stairs. I nearly fell trying to run down. I got to the next level just in time to see the door shut again. A crowd had exited, but the Massa was not among them.

I ran to the next floor. The bottom. I could smell burgers from a food court behind me. A sign pointed to the subway entrance. I heard the ding of the elevator, but it was a different door. A different car. I'd missed the one I'd been chasing.

"Pardon me, young man," said an old lady with an American Museum of Natural History hat. "Are you lost?"

"I'm looking for a guy in a robe," I said.

She nodded cheerily. "Ah yes, I just saw him."

"Do you know where he went?" I blurted.

"Of course." She pointed to a room with two wood-paneled doors, just beyond the food court. The guy was disappearing inside. I sprinted after him. "Yo!" I yelled as he entered the room. "Stop!"

A million words welled up from my gut and collided together in my brain. I was breathing so hard and fast I could barely speak. "I don't know . . . how you got here, but you . . . will never . . ."

The man turned. He was wearing thick glasses, a clerical collar, and a long black beard. "How I got here? Why, I took the C train. There is an exit from the platform-so convenient. Do you need directions, son? Have you lost your parents?"

That was when I noticed a name tag just below his collar: REV. JONATHAN HARTOUNIAN, MID-ATLANTIC ARMENIAN ORTHODOX COUNCIL. On a blackboard in the room behind him, someone had written GLIMPSES OF ARMENIAN RELIGIOUS CULTURE IN MODERN ARCHAEOLOGY. A crowd of bearded, black-robed guys turned in their seats, all staring at me with placid smiles.

"Um, sorry," I said. "So sorry . . ."

I backed into the hallway. Two kids were staring at me, holding tightly to their mom's hands. The old guide was approaching me with a curious expression.

Without a word, I turned for the stairway and ran.

I was losing it.

CHAPTER FORTY-FOUR.

THE SONG OF THE HEPTAKIKLOS.

"PROMISE YOU'LL STAY with us," Cass whispered over his shoulder as he climbed the basement stairs.

"Yes, Cass," I said wearily, "I promise."

"No chasing nice priests," he said.

"Ha-ha-ha," I said.

"Or being scared of beggars?"

"Knock it off!"

"Ssshh!" said Dad.

"Easy, Jack," Aly whispered. "We don't have a Loculus of Soundproofing."

We were walking fast, heading up from the lower level to the museum's first floor. At this point Cass was the only one holding on to the Loculus of Invisibility, which had hidden us nicely while the museum had closed for the night. But in a narrow stairwell it was hard for everyone to hold hands while one person held a Loculus, so Dad, Aly, and I were in plain sight. But that was fine. We'd snuck into a supply closet and found a custodial uniform for Dad. If someone did see us, Dad would say he was an employee and we were his niece and nephews from out of town, who he was showing around.

We gathered at the top of the stairs. The place echoed with the whine of distant vacuum cleaners. Just to be safe, we all held hands-Cass to Aly to me to Dad-and went invisible. We tiptoed through the empty Native American exhibit, under the disapproving frowns of dark totem poles that lined the aisles like trees in a forest.

At eight P.M., the museum had been closed for over two hours. We'd already seen a lot of the place, and I hadn't yet felt any sign of the Loculus of Healing. We were going to cover every inch until we did.

"Uh, guys, I have to go," Aly said.

"Go where?" Cass asked. "You have a hot date?"

"Go there, I mean." Aly gestured toward the restrooms.

As she headed in that direction, we all followed to maintain our invisibility.

We walked past a huge wooden longboat filled with Native American mannequins and a bear. To our left was a locked exit. Windows looked out to a circular driveway and a row of old apartment buildings across the street.

Aly gave us a raised eyebrow look. "Guys. You're not invited," she said.

"Not-wha?-we know!" Cass stammered. "We'll just, um, wait outside."

But then I began to feel a tingling in my feet. Then my knees. My heart started to thump.

"Wait a minute," I said. "It's here. The Loculus."

"In the bathroom?" Aly asked.

"Farther away," I replied. "But in this building. I feel it."

Aly's face lit up. "Go find it! Now. You, too, Mr. McKinley. Give me your phone, Jack. Cass and I will follow with the Loculi and catch up."

I fished out my phone and handed it to her. As Aly darted into the restroom and Cass vanished from sight, I went quickly into the next room. And the next. Dad followed close behind. Exhibits raced by us, but I hardly noticed. Rodents hanging on a wall. A roped-off exhibit in preparation. A stairway.

Floor Two. Secretary birds. African costumes. Antelopes.

The feeling was getting stronger, throbbing in the marrow of my bones, tickling the follicles of my skin. I stopped at the bottom of a dark stairway. "Up there," I said quietly.

At the base of the stairs was a sign on a brass post that said RESEARCH AREA/PERMIT REQUIRED. Dad slid it aside. "I think an exception to the rule can be made."

We scampered up the stairs and paused at the top, staring into a dimly lit hallway with closed doors on either side. Down at the far end was a T, two hallways leading left and right.

I froze. From the left hallway I could hear the steady tap-tap-tap of distant footsteps.

"Don't worry." Dad smoothed his uniform and began whistling softly.

Whistling?

"Why are you doing that?" I whispered.

"So they know someone's here and won't be startled when they actually see us," Dad said. "It'll be less suspicious. Now come on. Look like you belong."

I tried not to feel completely dorkish as we walked up the corridor. But the Song of the Heptakiklos was screaming inside me, pulling me forward. Telling me where to go. "Go right," I said through Dad's warbly whistle.

When we turned, we nearly collided with a woman in a simple custodial uniform, with her hair pulled back into a tight ponytail. "Howdy!" Dad said, way too loudly.

"Yesterday," the woman said.

"Huh?" Dad replied.

"The song you were whistling-'Yesterday,' by the Beatles-I like it." She looked closely at Dad's name tag. "How do you pronounce your name? Kosh . . . Koz . . ."

For the first time I saw the name tag on Dad's uniform: KOCIUSZKO.

"Koz!" I blurted out. "Everybody calls him Koz."

"This is my, er, nephew," Dad added. "Just giving him a little private tour."

"Nice to meet you," she said, pointing to her own tag, which read MARIA. "My name's easy."

"Well, Maria, we were just heading to grab something from room number . . ." Dad said, glancing toward me. "Room number . . . which one, young man?"

I didn't know!

It could have been any of the doors. There were three of them, one on each side and one at the end of the hallway. The sound was so unbearable I couldn't believe they weren't hearing it. I staggered closer. The room numbers swirled before my eyes-B23 . . . B24 . . . B25 . . .

I could feel Maria's gaze. "Is the boy all right?" she asked.

"Fine," Dad said.

"Fine," I said at the same time.

She suspects something's off. Pick a room. Any room. "B twenty-four!" I blurted out.

I bolted to the door and turned the knob, but it wouldn't budge.

Dad forced a chuckle. "That door is locked . . . um, Josh. We lock our doors here, heh-heh." He patted his pockets. "I, er, I think I left my key in my other pants."

"Very energetic young man," Maria said, fiddling with a lanyard around her neck. She stepped toward B24, holding out a plastic card. "Maybe he'll be a paleontologist someday."

What if that's not the right room?

I knew I might need to try them all.

"Can I do it?" I said. "Operate the key. I just want to see how it works."

Lame, lame, lame!

"That's a good idea," Dad piped up. "That way you can leave us here, Maria. James can open all the doors. We'll return your key to you."

Maria looked at him curiously. "I thought you said his name was Josh."

"He always makes that mistake!" I blurted out, grabbing the key and sliding it down the slot.

The door clicked open. It was a small meeting room with one long table, bookshelves, and a whiteboard. But I was interested only in the two file cabinets along the opposite wall. I raced over and pulled them open.

Papers. Folders. "It's not here," I said.

Now Maria looked alarmed. "What isn't?"

"Excuse me," I said, backing out of the room, into the hallway. Dad continued talking, chortling, grabbing her attention, stalling.

There. B25.

The room at the end had double doors. As I stepped closer, the Song cranked up to eleven. It was deafening.

"The Beatles' Abbey Road, actually, was my favorite album . . ." came Dad's cheery voice from down the hall.

I had to find the Loculus before he bored Maria to death.