Omaha nodded. “Okay, and what are you figuring?”

“We have to think in a context of ancient times. Something Cassandra failed to do, accepting modern miles for Roman ones. The answer lies in that fact.” Safia glanced back to him, testing him.

He stared at the wall, determined to solve this riddle. “The morning star is actually not a star. It’s a planet. Venus to be specific.”

“Identified and named by the Romans.”

Omaha straightened, then twisted to look at the artifacts. “Venus was the Roman god of love and beauty.” He knelt and touched the iron spear with the bust of the Queen of Sheba atop it. “And here’s a definite beauty.”

“That’s what I figured. So like at Job’s tomb, there must be a place to insert it. A hole in the ground.” She continued her search.

He joined her—but searched elsewhere. “You have it wrong,” he said. “It’s the wall that’s significant. Not the floor.” He ran his palm over the surface and continued his reasoning, enjoying the match of wits in solving this riddle. “It’s the slab that represents the morning star, so it is in the slab you’ll find—”

His words died as his fingers discovered a deep pock in the wall. Waist-high up the slab. It looked natural, easy to miss in the shadowy darkness. His index finger sank fully into it. He crouched there like the Dutch boy at the dike.

Safia rose up beside him. “You found it.”

“Get the artifact.”

Safia stepped over, grabbed the iron spear. Omaha pulled his finger free and helped her insert its end in the hole. It was an ungainly process with the wall angled. But they wiggled it into place. It kept sinking farther and farther. The entire haft of the spear was swallowed away, until only the bust was left, now hanging on the wall like some human trophy.

Safia manipulated it further. “Look how the wall is indented along this side. It matches her cheekbone.” She turned the bust and pushed it flush.

“A perfect fit.”

She stepped back. “Like a key in a lock.”

“And look where our iron queen is staring now.”

Safia followed her gaze. “The moon wall.”

“Now the heart,” Omaha said. “Does it belong to the sun wall or the moon?”

“I would guess the sun wall. The moon was the predominant god of the region. Its soft light brought cooling winds and the morning dew. I think whatever we’re looking for next, the final key or clue, will be associated with that wall.”

Omaha stepped to the north wall. “So the heart belongs to this wall. The sun. The harsh mistress.”

Safia glanced to the artifact. “A goddess with an iron heart.”

Omaha lifted the artifact up. There was only one place to rest it. In the small window cut into the northern slab face. But before settling it in place, he ran his fingers along the sill, having to stretch on his toes to feel the floor of the niche. “There are vague indentations in here. Like on the wall.” “A cradle for the heart.”

“A lock and key.”

It took a bit of rolling around to find the match between the iron heart’s surface and the indentations in the sandstone. He finally settled it in place. It rested upright. The end plugged with frankincense pointed at the moon wall.

“Okay, I’d say that’s an important slab,” Omaha said. “What now?”

Safia ran her hands along the last wall. “Nothing’s here.”

Omaha slowly turned in a circle. “Nothing that we can see in the dark.”

Safia glanced back at him. “Light. All the celestial bodies illuminate. The sun shines. The morning star shines.”

Omaha squinted. “But upon what do they shine?”

Safia backed up. She noted again the abnormally rough surface of the wall, its pocked moonscape. “Flashlights,” she mumbled.

They each retrieved one from the floor. Safia took a post by the mounted bust. Omaha moved to the heart in the window.

“Let there be light.” Holding the flashlight over his head, he positioned its beam as if it were sunlight pouring through the window, angled to match the position of the plugged end. “The sun shines through a high window.”

“And the morning star shines low on the horizon,” Safia said, kneeling by the bust, aiming her beam in the direction of the bust’s gaze.

Omaha stared at the moon wall, lit askance by their two light sources from two different angles. The imperfections of the wall created shadows and crevices. A form took shape on the wall, painted with these shadows.

Omaha squinted. “It looks like a camel’s head. Or maybe a cow’s.”

“It’s a bull!” Safia stared at Omaha, her eyes bright embers. “Sada, the moon god, is depicted as a bull, because of the beast’s crescent-shaped horns.”

Omaha studied the shadows. “But then where are the bull’s horns?”

The animal on the wall had nothing between its ears.

Safia pointed to the supplies. “Get me that while I hold the light.”

Omaha placed his flashlight in the window, resting it beside the iron heart. He crossed to the gear and grabbed the device that looked like a shotgun, only with one end belled out like a satellite dish. Safia had specifically asked Painter to bring it. He was anxious to see how this worked.

He passed it to her, taking her post with the flashlight.

She strode to the center of the room and pointed the laser excavator. A circle of red light appeared on the wall. She fixed it above the shadow figure, between the ears.

She pulled the device’s trigger. The red lights spun and sandstone immediately began to crumble as the laser energy vibrated the crystalline structure. Sand and dust billowed out. Also shinier bits. Flakes of metal, red.

Iron shavings, Omaha realized, understanding now why the metal detector was constantly abuzz. The architects of this puzzle had mixed iron shavings with the sand in the rock.

Back at the wall, the beam acted like a tornado, furrowing through the sandstone as if it were soft dirt. With his flashlight held steady, Omaha watched. Slowly, a brighter glitter revealed itself within the stone.

A mass of iron.

Safia continued to work, moving the laser up and down. In a matter of minutes, an arch of horns appeared, seated atop the shadowy image.

“Definitely a bull,” Omaha agreed.

“Sada,” Safia mumbled, lowering the gun. “The moon.”

She walked over and touched the rack of embedded horns, as if making sure they were real. A shower of blue sparks erupted with the contact. “Youch!”

“Are you all right?”

“Yes,” she said, shaking her fingers. “Just a static shock.”

Still, she backed a step away, studying the mounted horns on the wall.

The horns certainly appeared as a sharp crescent, protruding from the rock. Sand and dust cast from the excavation swirled into the chamber as the winds above grew suddenly more stiff, seeming to blow directly down through the hole in the roof.

Omaha glanced up. Above the sinkhole, the skies were dark, but something even darker stirred the air, sweeping downward. A light suddenly speared from it.

Oh, no…

10:47 A.M.

S AFIA FOUND herself grabbed around the waist and tackled to the side. Omaha dragged her into the shadows below the tilted slabs. “What are you—”

Before she could finish, a beam of bright light slammed through the hole overhead, casting a pillar of brilliance through the center of the trilith chamber.

“Helicopter,” Omaha yelled in her ear.

Safia now heard the vague beat of rotors against the dull roar of the storm.

Omaha held her tightly. “It’s Cassandra.”

The light blinked off as the floodlight swept away. But the thump of the copter’s rotors persisted. It was still out there, searching in the storm.

Safia knelt with Omaha. With the floodlight gone, the chamber seemed darker. “I have to alert Painter,” Safia said.

She crawled to the Motorola radio. As her fingers reached to its surface, another electric spark arced from radio to fingertips, stinging like a wasp. She jerked her hand back. Only now did she notice the escalation of static electricity. She felt it on her skin, crawling like ants. Her hair crackled with sparks as she glanced at Omaha.

“Safia, come back here.”

Omaha’s eyes were wide. He circled toward her, keeping to shadows. His attention was not on the helicopter, but fixed to the center of the chamber.

Safia joined him. He took her hand, shocking them both, hairs tingling.

In the center of the chamber, a bluish glow billowed where the helicopter’s beam had once shone. It shimmered, roiling in midair, edges ghostly. With each breath, it coalesced, swirling inward.

“Static electricity,” Omaha said. “Look at the keys.”

The three iron artifacts—heart, bust, and horns—shone a dull ruddy hue.

“They’re drawing the electricity out of the air. Acting like some lightning rods for the static charge of the storm above, feeding power to the keys.”

The blue glow grew into a scintillating cloud in the room’s center. It stirred to its own winds, churning in place. The keys shone even brighter. The air crackled. Traceries of charge coruscated from every fold of cloak or scarf.

Safia gaped at the sight. Sandstone was a great nonconductive insulator. Freeing the horns from the stone must have completed some circuit among the three. And the chamber was acting like a magnetic bottle, trapping the energies.

“We have to get the hell out of here,” Omaha urged.

Safia continued to stare, entranced. They were witnessing a sight set in motion millennia ago. How could they leave?

Omaha grabbed her elbow, fingers digging. “Saff, the keys! They’re like the iron camel at the museum. And now a ball of lightning is forming in here.”

Safia flashed back to the video feed from the British Museum. The ruddy glow of the meteorite, the cerulean roil of the lightning ball…Omaha was right.

“I think we just activated a bomb down here,” Omaha said, pulling Safia to her feet and shoving her to the collapsible ladder. “And it’s about to explode.”