Gray glanced back to the sunken garden, studying the professor’s path. “He was trying to keep out of sight.”

“Or maybe the guy was just hot,” Kowalski countered, wiping his sweaty brow.

Gray searched around. To the west, the Washington Monument pointed toward the blistering sun; to the east rose the dome of the U.S. Capitol Building.

Needing answers, Gray continued. The digital readout on the Gamma-Scout slowly faded as he crossed the Mall. With each step, he watched the millirems of radiation ticking downward.

Reaching the far side of the Mall, Gray hurried across

Madison Drive

. He picked up the trail again as it entered another park. The signal grew stronger as Gray neared a shadowy copse of red-twig dogwood and Natchez crape myrtles. A bench stood next to a knee-high bed of hydrangeas.

Gray stepped to the bench.

In the secluded spot, the millirems ticked up higher again.

Had Polk waited here? Was that why the residual radiation trace was stronger?

Gray shifted a flowering branch of a crape myrtle and found a wide view of the Mall stretching ahead, including a straight-on view of the Smithsonian Castle. Had the professor waited here until he thought it was safe? Gray squinted against the glare of the sun. He remembered Malcolm’s diagnosis, the debilitation, the wasting. Polk had been on his last legs. Desperation must have finally drawn him out.

Why?

Gray began to step away when Kowalski cleared his throat. He was on one knee, dusting a shoe, but his other arm reached under the bench. “Look at this,” he said and stood. Turning, he held a tiny pair of binoculars.

Gray shifted the detector closer to the scopes. The readings spiked higher. “They’re hot.”

Kowalski grimaced and thrust out the binoculars by their neck strap. “Take ’em, take ’em.”

Gray retrieved the binoculars. His partner’s fears were baseless. While there was radiation, it was only moderately worse than the usual background radiation.

Turning, Gray lifted the binoculars and peered through them toward the Castle. The view of the building swelled. He watched a figure pass along the front. Through the scopes, he made out the pedestrian’s features. Gray recalled Polk’s urgency when they’d neared each other. He’d dismissed it as a panhandler’s desperation for a bit of charity. He now suspected Polk had recognized him. Maybe it wasn’t solely desperation that had drawn him out. Had he spotted Gray crossing the Mall and come out of hiding to intercept him?

Gray dropped the binoculars into the lead-lined bag hung at his waist.

“Let’s go.”

Out of the copse of trees, Gray followed the trail west along

Madison Drive

to a set of steps.

The trail turned up them.

Gray lifted his head and found himself facing the Mall entrance to one of the Smithsonian’s most famous museums: the National Museum of Natural History. It housed a massive collection of artifacts from around the world—ecological, geological, and archaeological—ranging from tiny fossils to a full-scale T-rex.

Gray craned his neck. The museum’s dome loomed above a triangular portico supported by six giant Corinthian pillars. Staring upward, he was suddenly struck by how much the museum’s facade looked like the Greek temple on the professor’s coin.

Could there be a connection?

Before he followed the trail inside, he knew he’d better report in with central command. Stepping off to the side, he leaned on the stone balustrade and switched on his encrypted radio. He reached Director Crowe immediately.

“Have you found something?” Painter asked.

Gray kept his voice to a faint whisper. “Looks like the professor’s trail leads inside the Smithsonian’s natural history museum.”

“The museum…?”

“I’ll continue the search inside. But was there any connection between him and this place?”

“Not that I’m aware. But I’ll check into past associates.”

Gray remembered an earlier snippet of conversation about Dr. Polk’s past. “Director Crowe, one other thing. You never did explain something.”

“What’s that, Commander?”

“You said the professor invented Sigma Force. What did you mean by that?”

Silence stretched for a bit, then Painter continued. “Gray, what do you know about an organization called the Jasons?”

Taken aback by the odd question, Gray could not even fathom the context. “Sir?”

“The Jasons are a scientific think tank formed back during the Cold War. They included leaders in their respective fields, many Nobel Prize winners. They banded together to offer advice to the military elite about technological projects.”

“And Professor Polk was a member?”

“He was. Over the years, the Jasons proved to be of great value to the military. They met each summer and brainstormed on new innovations. And to answer your question, it was during one such meeting that Archibald Polk suggested the formation of a militarized team of investigators to serve DARPA, to act as field operatives for the agency.”

“And so Sigma was born.”

“Exactly. But I’m not sure any of this is significant in regard to his murder. From what I’ve heard so far, Polk’s not been active with the Jasons for years.”

Gray stared up at the towering Greek facade. “Maybe one of his fellow Jasons worked here at the museum? Maybe that’s why he came?”

“That’s a good point of investigation. I’ll look into it, but it might take some time to root out. Over these past few years, their organization has become more and more secretive. Divided among various top secret projects, Jasons don’t even know what other Jasons are doing nowadays. But I’ll keep making calls.”

“And I’ll keep following this trail.” He signed off and waved to Kowalski. “C’mon. We’re going inside.”

“About time we got out of the goddamn sun.”

Gray didn’t argue. Stepping through the doors, he appreciated the shadowy, air-conditioned interior. The museum was free to the public, but Gray flashed his glossy black I.D. card to the guard who manned the metal detector.

He was waved through.

Pushing into the main rotunda, Gray was struck by the sheer size of the space. The rotunda was octagonal in shape and rose three stories, each level lined by more pillars, leading to the massive Guastavino-tiled dome. Sunlight streamed through clerestory windows and a central oculus.

Closer at hand, in the center of the rotunda, stood one of the museum’s mascots, an eight-ton African bull elephant. It posed with raised trunk and curved tusks amid a field of dry grass. Polk’s path led around the elephant and toward a public staircase.

As Gray followed, he noted a banner hung high on the wall to the left. It advertised an exhibit opening next month. It depicted the head of Medusa, her hair wild with twisting snakes, reflected on a circular shield. Staring upward, Gray’s feet slowed.

He pictured Polk’s strange coin as he read the name of the upcoming exhibit, sensing he was on the right track.

LOST MYSTERIES OF GREEK MYTHOLOGY

6:32 P.M.

In the darkened room, the two men stared through the one-way glass into a child’s playroom. They sat in leather club chairs, while behind them climbed four rows of stadium seating, all empty at the moment.

This was a private meeting.

Beyond the mirrored glass, the neighboring room was brightly lit. The walls were painted white, with just the barest hint of sky blue, a color that from psychological statistics was supposed to encourage a calming, meditative state. It held a daybed with a flowered comforter, an open box of toys, and a child-size desk.

The older of the two men sat straight in his seat. At his side was a scuffed valise that held a disassembled Dragunov sniper rifle.

The other man, at fifty-seven years of age, was twenty years younger than his Russian companion. He slouched in a pressed suit. His eyes were fixed on the girl as she stood in front of a plastic easel and shuffled through a tray of pastel felt markers. She had spent the last half hour meticulously drawing a rectangle in green upon the white sheet of butcher paper attached to the easel. She had run the marker around and around in a hypnotically rhythmic pattern.

“Dr. Raev,” the man said, “I don’t mean to harp, but are you absolutely certain Dr. Polk did not have it on his person?”

Dr. Yuri Raev sighed. “I have spent my life on this project.” And my soul, he added silently. “I will not have it ruined when we are so close.”

“So then where is it? We turned over that cheap motel he stayed in last night. Nothing. It would raise too many questions if it should end up in unfriendly hands.”

Yuri glanced at the man in the neighboring seat. John Mapplethorpe, a division chief for the Defense Intelligence Agency, had a long face with sagging jowls and bags under his eyes, as if he were made of candle wax and been left too long in the sun. Even the dye he used on his hair was too dark, too obvious a vanity for his age. Not that Yuri had any right to fault a man for attempting to stem the tide of age. Beneath the sag of his own skin, Yuri’s body remained toned, his reflexes sharp, and his mind as quick and agile as it ever had been. Between injections of androgens and growth hormone, along with vigorous exercise, he fought as adamantly as anyone to hold back time. But it was not vanity that drove him.

He stared into the room.

No, not vanity.

Mapplethorpe drummed his fingers on the arm of his chair. “We must recover what Polk stole.”

“He did not have it with him,” Yuri assured Mapplethorpe more forcefully. “It is too large to conceal on his person, even under a jacket. I was fortunate to stop him when I did. Before he spoke to anyone.”

“I hope you’re right. For all our sakes.” Mapplethorpe turned his attention back to the room. “And she was able to track him? All the way from Russia.”

Yuri nodded. Fatherly pride entered his voice. “With her and her twin brother, we may have finally breached the barrier.”

“Too bad she couldn’t have been quicker.” Mapplethorpe made a dismissive sound. “My brother-in-law’s daughter has an autistic boy. Did I ever tell you that? But he’s not an idiot savant. He can hardly tie his shoes.”