“I don’t love that,” Lavinia muttered.

I looked down at my ukulele, wishing I’d brought a bigger instrument to hide behind. A stand-up bass, perhaps. “How do we get in?”

I hoped the answer would be Gosh darn it, we can’t.

“There.” Hazel pointed to a section of concrete that looked no different from the rest.

We followed her over. She ran her fingers across the dark surface, leaving glowing silver grooves that outlined a rectangular slab the size of a coffin. Oh, why did I have to make that particular analogy?

Her hand hovered over the middle of the rectangle. “I think I’m supposed to write something here. A combination, maybe?”

“To open his door,” Lavinia recalled, “two-fifty-four.”

“Wait!” I fought down a wave of panic. “There are lots of ways to write ‘two-fifty-four.’”

Hazel nodded. “Roman numerals, then?”

“Yes. But two-five-four would be written differently in Roman numerals than two hundred and fifty-four, which is different from two and fifty-four.”

“Which is it, then?” Meg asked.

I tried to think. “Tarquin would have a reason to choose that number. He’d make it about himself.”

Lavinia popped a small, stealthy pink bubble. “Like using your birthday for your password?”

“Exactly,” I said. “But he wouldn’t use his birthday. Not for his tomb. Perhaps his date of death? Except that can’t be right. No one’s sure when he died, since he was in exile and buried in secret, but it had to have been around 495 BCE, not 254.”

“Wrong date system,” Meg said.

We all stared at her.

“What?” she demanded. “I got raised in an evil emperor’s palace. We dated everything from the founding of Rome. AUC. Ab urbe condita, right?”

“My gods,” I said. “Good catch, Meg. 254 AUC would be…let’s see…500 BCE. That’s pretty close to 495.”

Hazel’s fingers still hesitated over the concrete. “Close enough to risk it?”

“Yes,” I said, trying to channel my inner Frank Zhang confidence. “Write it as a date: Two hundred and fifty-four. C-C-L-I-V.”

Hazel did. The numbers glowed silver. The entire stone slab dissipated into smoke, revealing steps leading down into darkness.

“Okay, then,” Hazel said. “I have a feeling the next part is going to be harder. Follow me. Step only where I step. And don’t make any noise.”

Meet the new Tarquin

Same as the old Tarquin, but

With a lot less flesh

SO…NO JOLLY TUNES on the ukulele, then.

Fine.

I silently followed Hazel down the steps into the merry-go-tomb.

As we descended, I wondered why Tarquin had chosen to reside under a carousel. He had watched his wife run over her own father in a chariot. Perhaps he liked the idea of an endless ring of horses and monsters circling above his resting place, keeping guard with their fierce faces, even if they were ridden mostly by mortal toddlers. (Who, I suppose, were fierce in their own way.) Tarquin had a brutal sense of humor. He enjoyed tearing families apart, turning their joy into anguish. He was not above using children as human shields. No doubt he found it amusing to place his tomb under a brightly colored kiddie ride.

My ankles wobbled in terror. I reminded myself there was a reason I was climbing into this murderer’s lair. I couldn’t remember what that reason was at the moment, but there had to be one.

The steps ended in a long corridor, its limestone walls decorated with rows of plaster death masks. At first, this did not strike me as odd. Most wealthy Romans kept a collection of death masks to honor their ancestors. Then I noticed the masks’ expressions. Like the carousel animals above, the plaster faces were frozen in panic, agony, rage, terror. These were not tributes. They were trophies.

I glanced back at Meg and Lavinia. Meg stood at the base of the stairs, blocking any possible retreat. The glittery unicorn on her T-shirt grinned at me hideously.

Lavinia met my eyes as if to say, Yes, those masks are messed up. Now, keep moving.

We followed Hazel down the corridor, every clink and rustle of our weapons echoing against the barreled ceiling. I was sure the Berkeley Seismology Lab, several miles away, would pick up my heartbeat on their seismographs and send out earthquake early warnings.

The tunnel split several times, but Hazel always seemed to know which direction to take. Occasionally she’d stop, look back at us, and point urgently to some part of the floor, reminding us not to stray from her path. I didn’t know what would happen if I took a wrong step, but I had no desire to have my death mask added to Tarquin’s collection.

After what seemed like hours, I began to hear water dripping somewhere in front of us. The tunnel opened into a circular room like a large cistern, the floor nothing but a narrow stone path across a deep dark pool. Hooked on the far wall were half a dozen wicker boxes like lobster traps, each with a circular opening at the bottom just the right size for…Oh, gods. Each box was the right size to be fitted over a person’s head.

A tiny whimper escaped my mouth.

Hazel glanced back and mouthed, What?

A half-remembered story floated up from the sludge of my brain: how Tarquin had executed one of his enemies by drowning him in a sacred pool—binding the man’s hands, placing a wicker cage over his head, then slowly adding rocks to the cage until the man could no longer keep his head above water.

Apparently, Tarquin still enjoyed that particular form of entertainment.

I shook my head. You don’t want to know.

Hazel, being wise, took my word for it. She led us onward.

Just before the next chamber, Hazel held up a hand in warning. We halted. Following her gaze, I could make out two skeleton guards at the far side of the room, flanking an elaborately carved stone archway. The guards faced each other, wearing full war helmets, which was probably why they hadn’t spotted us yet. If we made the slightest sound, if they glanced this way for any reason, we would be seen.

About seventy feet separated us from their position. The floor of their chamber was littered with old human bones. No way could we sneak up on them. These were skeleton warriors, the special forces of the undead world. I had zero desire to fight them. I shivered, wondering who they had been before the eurynomoi stripped them to the bones.

I met Hazel’s eyes, then pointed back the way we’d come. Retreat?

She shook her head. Wait.

Hazel shut her eyes in concentration. A bead of sweat trickled down the side of her face.

The two guards snapped to attention. They turned away from us, facing the archway, then marched through, side by side, into the darkness.

Lavinia’s gum almost fell out of her mouth. “How?” she whispered.

Hazel put her finger to her lips, then motioned for us to follow.

The chamber was now empty except for the bones scattered across the floor. Perhaps the skeleton warriors came here to pick up spare parts. Along the opposite wall, above the archway, ran a balcony accessed by a staircase on either side. Its railing was a latticework of contorted human skeletons, which did not freak me out at all. Two doorways led off from the balcony. Except for the main archway through which our skeleton friends had marched, those seemed to be the only exits from the chamber.