Nora followed as her father led her and Maria to a corridor that was wide and well lit.

This area of the bunker seemed to be some kind of office complex. There were doors on each side of the hall, and when she passed an open one, Nora saw an open-concept team room with desks that were mostly empty.

On the whole, she got the impression that this was a shelter waiting to be occupied.

Perhaps the most surprising aspect of this place was that it had power. Did burying it this deep put it out of reach of the Covenant’s electromagnetic ordnance? It would seem so.

Nora’s father rounded a turn and marched past four armed guards standing by a set of double doors, which led to an auditorium. The room had stadium seating capable of holding what Nora estimated would be a hundred people.

Far fewer were present. Perhaps twenty individuals sat in the rows. On the stage below, a lectern waited, bright lights shining down on it.

Nora was reminded of her recent talk at Oxford, of the announcement of The Birthright. She marveled at the fact that she had given that speech only a few days ago, yet it felt to her like a million years.

“Take a seat anywhere,” Robert said before he made his way to the lectern, where he conversed with the man and woman there and then tapped a control panel that dimmed the lights.

A beam lanced out from the back of the room, displaying an image on the screen, a black background with white letters that read PROJECT POSEIDON.

Robert stood in the center of the stage, surveying the crowd. When the room fell silent, he reached into the lectern and took out a small round

controller with a single button and a thick cord that ran back to the lectern. It reminded Nora of a jump rope and its handle.

When her father clicked the button, there was a mechanical shuffling sound at the back of the room as the projector rotated the next slide into place. Nora marveled that while the bunker was like a dark dystopian future, the technology inside was much like the 1960s.

Robert’s voice boomed in the auditorium.

“When I was a child, I learned a fact that changed my life. Telling you that fact now will reveal just how odd a young man I was.”

He smiled, and motioned to the image behind him, which showed a global map with the landmasses in gray and yellow rings around the coastline. There was also a faint yellow line at the equator. The oceans were shades of blue, and the colors got darker toward the center of the seas, away from land and the equator.

“The fact that changed my life was that somewhere between fifty and seventy percent of the oxygen in the Earth’s atmosphere comes from the sea. I had always thought that the forests and the trees and plants around us were responsible for the air we breathe, but they are only a bit player in the oxygen cycle upon which life on this planet depends. The true star of Earth’s oxygen cycle is phytoplankton, a group of organisms that includes photosynthesizing bacteria and plantlike algae. Most phytoplankton are too small to be seen by the unaided eye. They live principally on the surface of the sea, where they capture sunlight and use its energy to split carbon dioxide and water, making sugar for themselves and releasing oxygen as a by-product. And they release a lot of oxygen. Phytoplankton alone account for about half of global photosynthetic activity and about half of the oxygen production, yet they represent only about one percent of the global plant biomass. And unlike trees and other plants that live for years—sometimes hundreds of years—phytoplankton have a life cycle measured in days.”

Robert paused. “As a child, that fact fascinated me. I thought: here is a mostly unseen organism that controls the fate of our world, the very air we breathe. It floats at the top of the seas and lakes and streams, blown by the wind and carried by the currents, and its destiny is our destiny, and we should try to understand it and ensure that it flourishes. Its destiny is linked to ours. That’s why I became a marine biologist. I believed that the seas were the key to securing humanity’s future.”

He clicked the small controller. An image appeared that showed what Nora recognized as a slide from a microscope, a view of a viral particle.

“It’s funny how life has a way of distorting your dreams. I saw in the seas a way to protect future generations. Today, I still believe the seas are our key to survival, but in a far different way.”

Robert took a deep breath. “In less than a week, the Covenant will launch a new wave of missiles—the A21. We don’t know precisely what their new ordnance is. We know only that it will wipe us from the face of the Earth forever.”

He set the small controller on the lectern and paced on the stage. “The Covenant has taken our ability to use advanced electrical technology. They’ve relegated us to the Stone Age. They think we don’t have a way to fight back. They are wrong.”

He nodded. “Sure, our weapons are no match for them. Nor are our numbers. At this point, they probably see us as a nuisance to get rid of. But we have one last way to fight back: biology. Biology doesn’t depend on electricity. Or advanced technology. And it is the most powerful weapon on Earth.”

He pointed to the image of the viral particle behind him. “What you’re looking at is the key to our survival. It’s something I never dreamed I would help create. A pathogen to kill the seas—a virus that, within days, will kill virtually all of the planet’s phytoplankton. We call it the Poseidon virus, and it will be carried by the fish in the tank you all walked past just a few moments ago.”

Robert shook his head. “In a way, my childhood dreams are coming true. I am using my love and knowledge of the sea to save humanity. I simply never imagined the cost.”

He returned to the lectern and took the controller and clicked the next slide, but Nora found it nearly impossible to focus on it. Her heart was beating in her ears, chest heaving. She couldn’t believe what she was seeing. It was impossible, the dark future her father was about to usher in.

“I know what you’re thinking,” he said, voice booming in the auditorium. “How does killing the phytoplankton save us? The answer is simple: in a matter of days, Earth’s fragile ecosystem will be irreparably altered. In particular, the production of oxygen will plummet—I estimate by at least half. Now, I can imagine your next question, that it won’t affect the atmosphere for some time. And you’re right. The atmosphere is vast, and it

takes time to cycle completely. But the thing is, it doesn’t take much for this planet to become uninhabitable.”

He motioned to the image of a drawing of a human body and a chart that showed oxygen levels from green to red. “The air we breathe is about 78 percent nitrogen gas, 20.9 percent oxygen, and the remaining 1 percent is primarily argon gas with trace amounts of carbon dioxide, neon, and helium. A human needs a minimum oxygen concentration of 19.5 percent to breathe effectively. The lungs take in air, separate out the oxygen and use red blood cells to carry that oxygen throughout the body. Every cell requires oxygen to function—and without it, they begin to degrade. At lower than

19.5 percent oxygen, mental and physical performance will degrade. Humans will tire faster. Below 14 percent, thinking will become even more difficult. Respiration will be intermittent. At lower than 6 percent oxygen in the air, no human can survive.”

Robert looked up at the ceiling. “So after the phytoplankton are gone, how long will that take? The short answer is that we’re not sure. We think a few years. Keep in mind that the death of the phytoplankton won’t only affect the oxygen levels—it will impact CO2 levels as well. Without

phytoplankton to remove carbon dioxide from the atmosphere, the planet will become warmer.”

He inhaled, a deep lungful of oxygen-rich air that Nora now saw in a completely different way. “While I don’t know the exact timeline—that is, how long it will take humans to perish after the phytoplankton are gone—I know it will happen. And I know we will be safe down here. Here in these arcologies, we have massive oxygen concentrators and scrubbers that will provide for our needs. We have farms where we can grow food to sustain us.” He paused. “What has given us this opportunity is a simple shift in thinking. Where we once saw disadvantages, we searched for strength. In a world choking to death, having a small population, and being underground, is an advantage. In a world where we can’t have electronic technology, mastery of biology becomes the key to survival. And we will survive, thanks to Project Poseidon—and that’s precisely what you are here to vote on. A no vote will be the last you ever cast. This is our final chance to strike back, to give our children a future on this Earth. I’ll take questions now.”

Murmurs erupted across the auditorium.

Nora’s father’s gaze settled on her before she had a chance to wipe the shock from her face. In that split second, she knew that he saw it, and that it

surprised him. He squinted, studying her. Nora knew what he was seeing: that she was indeed an impostor.

He stared at her, his expression a mix of confusion and hurt.

Nora placed her hand on Maria’s arm, gripped it, and motioned back to the closed double doors behind them, where she knew the soldiers stood guard.

She had to get out.

But when she glanced back down at the stage, her father locked eyes with her and gave a sharp jerk of his head to the side, the meaning clear: Don’t go anywhere.