The Kill Switch

Bukolov’s eyes danced, as if this last part was significant. When Tucker didn’t question him, the doctor gave him an exasperated look and continued. “Not only is this the kill switch, but it explains why the genetically superior LUCA did not survive the Archean eon, but cyanobacteria did.”

“What’s the answer?”

“One of the turning points of that primordial era to the next was a shifting of atmospheric conditions, an acidifying of the environment. Remember, back then, oxygen-producing plants did not exist. It was a toxic hothouse. Acid rain swept in great swaths over the earth, tides and storms burned with it.”

“And that’s important why?”

“Cyanobacteria were perfectly equipped to deal with this acidification of the environment. They were already masters of organic chemistry, as evidenced by their control of photosynthesis, a process of turning sunlight into chemical energy. They rode that acid tide and adapted. Unfortunately, LUCA’s mastery was in the field of genetics. It placed all its evolutionary eggs in that one basket—and chose wrong. It could not withstand that tidal change and stumbled from its high perch in the food chain. And like sharks sensing blood in the water, cyanobacteria took advantage, incorporating that acid into their makeup and burning LUCA out of the last of its environmental niches, driving it into evolutionary history.”

Bukolov pointed to the steaming dark brown mire in the beaker. “That’s the acid.” A single drop splashed from the distillation pipe into the soup. “That’s what passed for rain long before we were even single-celled organisms floating around in mud. What we’re brewing here is a form of precipitation that hasn’t been seen for 3.5 billion years.”

“And that will kill LUCA.”

“Most definitely.” Bukolov stared at him. “But even still, we must catch any such environmental fires started by LUCA early, preferably as soon as they’re set. Once it establishes a foothold and reaches critical mass, it will explode across an environment, a raging firestorm that even this ancient rain might not put out.”

“So if we’re too late stopping Kharzin, even this might not be enough.”

Bukolov slowly nodded, watching the slow drip of acid. “The only good news is that we ran some preliminary estimates of the threat posed by the single bulb Kharzin possesses. In the long term, he could, of course, try to grow more bulbs, but that would take much patience.”

“A virtue Kharzin is sorely lacking.”

“In the short term, we estimate he could macerate and extract at best a liter or two of weaponized LUCA. But it’s still enough to light a fire somewhere, a fire that would quickly become a storm.”

So the only question remains: Where does he strike that match?

To answer that, Tucker had only one hope.

In the shape of a deadly assassin.

And so far, she was not being cooperative.

9:12 A.M.

“Felice Nilsson could have scrubbed her credit cards,” Harper told him over the phone.

Tucker spoke to her as he crossed in long strides from Bukolov’s lab and headed across Fort Detrick’s campus for his dormitory. “Like I said from the start, Harper. It was a long shot.”

Three days ago, he had informed Sigma about his radioed conversation with Kharzin and the conspicuous absence of a certain someone to that deadly party in the mountains of Africa. Kharzin had claimed Felice was on another assignment, which even back then struck him as odd. She had been Kharzin’s point man in the field from the start, hounding Tucker since he’d first set foot aboard the Trans-Siberian Railway. Then as Kharzin’s team closed in for the kill, she was suddenly pulled off and reassigned.

Why? And to where?

Tucker had proposed that perhaps Kharzin had pointed that particular blond spear in a new direction, sending her in advance to prepare for the next stage of his plan—and likely to execute it, too.

“It was a good idea,” Harper said. “To search for her whereabouts by placing a financial tracer on her. But so far we’ve failed to get any hits from the documents you photographed aboard the train. Not the four passports, not the five credit cards, not even the bank routing numbers you managed to find. She likely received a new set of papers.”

Sighing, Tucker ran through his steps that day as he broke into her berth. He had carefully sifted through her belongings, photographed what he found, and returned everything to where he’d found them.

“Maybe I wasn’t careful enough,” he said. “She must have gotten wise to my trespass.”

“Or she could have just gone to ground and is keeping her head low. We’ll keep monitoring.”

1:22 P.M.

Tucker briefly visited Bukolov after lunch and discovered the doctor was working with an engineer, devising an aerosol dispersal system for his acid solution, which to him looked like a backpack garden sprayer. But he heard phrases like flow rate composition and contaminant filter thresholds, so what did he know?

Bukolov had little time to chat, so Tucker left and decided to do something more important.

Standing on a windswept wide lawn, he hauled back his arm and whipped the red Kong ball across the field. Kane took off like a furry arrow, juking and twisting as the ball bounced. He caught up to it, snatched it in his jaws, and did a little victory prance back to Tucker’s side, dropping the ball at his toes. Kane backed up, crouching his front down, his hind end high, tail wagging, ready for more.

It was good to see such simple joy—though obsession might be the better word, considering Kane’s current deep and abiding love for that rubber Kong ball. Still, the play helped temper the black cloud stirring inside Tucker.

If only I’d been more careful . . .

Tucker exercised Kane for another few minutes, then headed back to their dorm. As he crossed the lawn, his phone rang. It was Harper again.

“Looks like you have a future career as a cat burglar after all, Captain Wayne. We got a hit on Ms. Nilsson.”

“Where?”

“Montreal, Canada. Hopefully you and Kane are up for a little more cold weather.”

He pictured Felice’s face, remembering Utkin in the sand, bloody and crawling.

“I’ll grab our long johns.”

43

March 28, 10:23 A.M.

St. Ignace, Michigan

Right back where I started . . .

Tucker stood on the hotel balcony, staring out at the frozen edges of Lake Huron. Snow sifted from a low morning sky. The rest of the view could best be described as brittle. It was below freezing with the forecasted promise of the day climbing a whole two degrees.

He’d started this adventure in Vladivostok, a frozen city by the sea.

And here he was again: cold and facing another assassin.

Bukolov called from inside the room. “Some of us don’t have the hardy constitution of a young man. Perhaps if you close the balcony door, I won’t catch pneumonia before your tardy guest arrives in the area.”

He stepped back inside and pulled the slider and latched it. Kane lifted his head from where he curled on the bed.

“But for the hundredth time, Doc: you didn’t have to come.”

“And for the hundredth time: you may need my expertise. We have no idea how Kharzin plans to utilize his weaponized LUCA. And my solution has had no real-world field test. We may have to improvise on the fly. Now is not the time for inexperienced guesswork.”

It had been two days since Sigma’s cyber net had detected the credit card hit in Montreal. Unfortunately, Felice still remained a ghost, leaving only the occasional financial bread crumb behind: at a gas station outside of Ottawa, at a diner in the small town of Bracebridge. Her movements seemed headed straight for the U.S. border. Immigrations and Customs were alerted, but the northern border of the United States was an open sieve, especially in the dense woods nestled among the Great Lakes. She could easily cross undetected.