The Navy Memorial was spread out on her right beyond the fountains separating it from the sidewalk. A former Navy girl herself, Teresa liked to refer to the memorial as proof that the US is at the center of the globe. The joke was a tongue-in-cheek jab at the large map of the world stretching across the concrete, with North America clearly defined in the center and the other continents fading out around it. And at The Lone Sailor-a Navy man, of course, standing over it.

West of the memorial, Teresa ignored the signal at Ninth Avenue and dodged traffic as she headed across the street toward the main entrance of J. Edgar Hoover Building. As she did, her cell phone rang.

"s.h.i.t," Teresa muttered through the half-masticated food in her mouth. Hurrying to swallow, she absently wiped her face as if her caller could see her. When she could speak somewhat clearly, she answered the phone, "Wood here."

"Teresa!"

Her caller sounded a little distressed. "Ken?" she asked.

"Yeah, it's me," said her colleague from the graphics department. "You're not going to believe this."

"Ken, I'm in D.C. I have a prioritization meeting at FBI headquarters." She dusted the remaining hot dog crumbs off of her suit jacket where they had come to rest upon her sizable b.r.e.a.s.t.s.

"Well, they're going to want to see this, too. It's going to change some of your prioritizations. Look at this."

Teresa's cell phone clicked as Ken hung up. Bewildered, Teresa stared at the face of the phone for a moment until it began to vibrate. A bubble on the screen indicated a new text message.

Teresa opened the message. The small embedded graphic was one she had seen the previous day for the first time. The little bouquet. How cute, except that it came with the threat of a nationwide terrorist attack by ISIL.

As Teresa began reading Ken's text message beneath the image, her rapid pace toward FBI headquarters slowed to a standstill. Her heart began to thud in her chest and she sank heavily onto a nearby bench.

"Holy Christ," Teresa said aloud, still staring at the screen of her phone.

Katrina's hands flew up as she stood wide-eyed behind her desk, panting. "What!" she practically shouted, her eyes moving from one agent to the other.

"Explain this!" Gilman spat, throwing a sheet of paper down onto her desk.

Katrina slowly and deliberately reached for the page, watching the agents and the guns pointed toward her. She picked the paper up with hands that were now trembling. On one side of the page was a black-and-white copy of the image on Katrina's wall. On the other was a long message handwritten in Arabic script.

"I can't explain it," Katrina said. "I don't speak the language." Before laying it back down, she flipped it over to glance once again at the picture.

"Where did you get that?" McMullan asked, jabbing a thumb backward to indicate the poster.

"Nature," she replied.

"Very funny," said Gilman. "It's a computer graphic."

Despite her trepidation at the guns still pointed in her direction, Katrina suppressed a smile. "I meant Nature"-she bent the first two fingers of both hands in the air to simulate quotation marks-"the scientific journal." She then pointed for emphasis to a printed issue on her desk of the same publication.

McMullan and Gilman lowered their guns. Gilman picked up the journal and flipped through quickly. Katrina gestured to a section of one of the built in bookshelves on the wall next to the desk, where she had three entire shelves dedicated to the same publication.

"What would this... artwork... be doing in a scientific publication?" Gilman demanded.

"It's not artwork," Katrina said.

McMullan stammered. "You mean, anyone who has read this particular... journal... entry, or whatever, would have seen this picture?"

"Of course," Katrina said. "Any half-decent anthrax researcher will absolutely know this paper. In 2004, it was arguably the biggest accomplishment in the field." Her eyes darted from one FBI agent to the other as they sat down in front of her desk once again.

Gilman reached back into his briefcase and pulled out another sheet of paper. Looking back at McMullan, who nodded his approval, he handed it over to Katrina.

"OK, Dr. Stone," he said, "this is the English translation of the Arabic text you just looked at. The original image and text came from a greeting card received at the White House on the same day that the activated strain of anthrax was discovered. Now, what does the bouquet on your wall have to do with either of those events?"

Katrina skimmed over the English translation of the card. "Gentlemen," she said slowly. "This is not a graphic image of a bouquet. It is a crystal structure detailing a molecular mechanism. What you are looking at is the membrane pore formed by anthrax toxins upon interaction with their host cell receptor. This is the structure that allows infiltration of anthrax into a human cell."

2:07 P.M. PDT.

"If you promise not to shoot me, I'll show you," Katrina said with a bit of sarcasm.

The agents finally holstered their weapons.

Katrina sat back down at her desk and clicked into the reference library in her computer, then grabbed a yellow Post-It note and a pen. She quickly wrote "Santelli, E. (2004) Nature 430: 905." Then she stood and walked to the bookshelf, from where she selected the appropriate issue of the journal. With both agents looking over her shoulder, she flipped to page 905. Katrina turned two more pages to reveal another full color print of the same image.

"There, you see?" She set the journal on the desk and walked to the wall poster. Pointing at one of the brightly colored cl.u.s.ters, she said, "I know; it does look like flowers. See these seven pieces?"-she encircled each of the differently colored groupings with a forefinger-"the flower heads, if you will? They're all identical to each other. These are called subunits. Each is one copy of an anthrax protein called protective antigen. It interacts with a receptor produced by the host cell, shown here." She traced the neatly arrayed hollow cylinder protruding downward. "The receptor is what looks like the stems of the flowers, but it is actually a pore. When the anthrax proteins interact with the receptor, this pore shuttles the lethal factor toxin into the cell, and that is where the toxin's effects are exerted."

"Why would the cell do that?" Gilman asked, incredulous. "It's as if the cell commits suicide by bringing these toxins inside, right?"

"For lack of a better way to say it," she responded, "the cell doesn't know any better. The receptor is a normal cell surface protein. Its job, so to speak, is to bring beneficial molecules inside. The anthrax proteins infiltrate by hijacking the machinery, so the cell brings the toxin inside instead."

"What do the toxins do to kill the cell?" McMullan asked.

Katrina shook her head and looked down at the floor. "We still don't know," she said. "Despite all the research that has been conducted since 9/11, we still don't know exactly how anthrax kills people."

In Washington, D.C., Teresa Wood sat with White House Postal Operator Jack Callahan and FBI Case Director Bob Wachsman. The three of them were reviewing her colleague's brief for a second time.

"It was never flowers at all," Teresa said.

Jack nodded. "And I think we can be a.s.sured of three things: that the greeting card was not a hoax, that the activated anthrax strain is the threat referred to in that card, and that what happened at San Quentin four days ago is going to happen to the rest of us on Christmas Day."

2:56 P.M. PDT.

After the two FBI agents left her office, Katrina sat at her desk waiting for her heart rate to return to normal. The words of Agent Sean McMullan were echoing through her mind. A new strain of anthrax has been discovered, and this strain contains an unusual element.

Katrina took several deep breaths and let them out slowly. She grabbed a Kleenex from the box on her desk and blotted her perspiring face. There is a plasmid incorporated into its DNA that encodes a potent activator of anthrax lethal factor. She stood and stepped out of her office. It was Jason she needed to see.

Oxana was still in the main lab. Katrina approached her and spoke with her quietly for a few moments. Then she pa.s.sed through the main lab and entered the robot room. As if to say h.e.l.lo, Octopus swung an arm toward her. It picked up a reaction plate and filed it away into the incubator as Katrina swerved around it and walked through to the cell culture room.

Jason Fischer and Todd Ruddock were inside. Jason sat before a laminar flow hood, dousing every square inch of its works.p.a.ce with ethyl alcohol from a squirt bottle.

Katrina came up behind him. "Fischer! You are an alcoholic!"

"Heh heh. Well, if I'm not at the bar, I'm sterilizing something."

"It is good for all occasions that way."

"What's up?" he asked without turning around. He wiped up the ethanol with stack of paper towels and then threw the towels into a bright red Biohazard Waste can.

"I was wondering how late you're planning on working tonight and what you have planned when you're done."

"I still have to feed my cells," he said and uncapped a bottle to begin transferring liquid into a small plastic dish. "I'm just getting started and it'll take me, um, probably about an hour."

"And then?"

"Hmm," he stuck his nose in the air and mused in a horrible British accent, "I think maybe I'll take the yacht out for a spell."

Katrina chuckled and poked her finger through a gaping hole in his faded black sweatshirt. "Maybe you oughta sell your yacht and buy some clothes, dude," Katrina said.

"Actually, I'm going home afterward," Jason said, dropping the British accent. "I feel c.r.a.p-tacular. And I like my clothes just the way they are, thank you! They dispel the grossly unjust myth that everyone with a Ph.D. makes a s.h.i.tload of money."

"They also dispel the myth that everyone with a Ph.D. is a stuffy geek," Katrina commented.

"As do you," Jason said with a smile.

Katrina thought Jason looked pale, and his face was covered with perspiration despite the cool temperature in the room. "Now that you mention it, you look c.r.a.p-tacular," she said.

Jason looked up at her and raised one eyebrow.

"No offense," she added.

"None taken."

"Rough night last night? You had a show, didn't you?"

"Yeah, but if this is a hangover it's the worst one I've ever had in my life. I think I have the flu. I woke up with it this morning. I'm getting some serious rest this weekend."

Todd Ruddock stood up from where he had been sitting at the adjacent hood and took a tray out of an incubator. He laid the tray on the counter next to the microscope and began picking up culture plates one at a time to inspect them under the scope.

Katrina kept talking to Jason. "d.a.m.n. I need to talk to you. I was hoping to take you out for a beer."

"Am I in trouble?"

"Haha, no. Actually, I want to talk to the whole lab. There's been a bit of a development. It's a long story; hence the beer idea."

She posed the same question to Todd. "Hey, Todd, are you free in about an hour for a beer?"

"You buying?"

"Yep."

"Um, let me think. Yes." Evidently satisfied with what he saw under the scope, Todd returned the tray of culture plates to its shelf in the incubator, nodded at Katrina, and breezed out of the room.

Katrina watched Todd walk through the robot room and back into the main lab. Then she closed the door. "Jason, listen," she said.

Jason finally stopped working and turned from the hood to face her, his face questioning. Katrina never closed doors.

She glanced through the window and into the robot room one more time before speaking. "Where is the activator data, and how many people know about it?"

3:12 P.M. PDT.

McMullan and Gilman were quiet as they drove away from Katrina Stone's lab. When McMullan finally broke the silence, his words seemed out of place. "She's an anthrax researcher!"

"Yeah, I figured that much out," Gilman responded. "So?"

"So, Homeland Security has her entire life on file."

Gilman smiled for the first time since being a.s.signed to this case.

Jason had never seen Katrina so poorly composed. Her face was flushed, and she looked as if she, too, had been sweating. Jason wondered if she could be coming down with the same bug he had woken up with at the annoying groupie's house. It would be no surprise. Between the close quarters within the lab, the excessive workload, and the lack of rest they were all burdened with, when one person got sick, the whole lab usually caught it.

He did not answer her question right away.

"Well, I have talked to people about the data," Jason finally said, "right after I found the activator. I found it, like, a week before the Keystone conference, remember? So I was sitting with a group of anthrax people at the conference during lunch one day, and something came up that made me think of it." He paused long enough to raise an eyebrow. "I didn't think it was a secret."

Katrina said nothing.

"A bunch of the people at the table were doing inhibitor screens like ours," Jason continued, "looking at all different types of molecules. I mentioned that we had stumbled upon some activators of lethal factor while we were looking for inhibitors. Some of the other people said they had seen them, too. I guess it's pretty normal, every once in a while, to come across something that activates the enzyme. But n.o.body had seen the three-hundred-fold increase in lethal factor activity we saw with the 37B-17 compound.

"I remember this guy from Stanford said, 'Well, if you ever want to make a biological weapon you're all set.'"

Katrina visibly bristled.

Jason remembered having made a similar remark the day he found the activator. He had gone to her office to discuss his inhibitor data, and in the course of the conversation he had mentioned the activator as an offhand remark. To Jason's surprise, she had asked him to elaborate. He told her that there were several, but that one in particular was extraordinarily potent.

"Keep the data and set the compound aside," she had instructed him. "If we aren't finding any really good inhibitors, we may want to talk to the chemists. A minor structural change can potentially convert an activator into an inhibitor. So we might still be able to use it... "