It's a tough task to stand out in today's crowded speculative fiction literary market with its healthy spectrum of military sci-fi, space opera, and fantasy/horror hybrids for readers of all persuasions to choose from.

However, an absorbing new science fiction thriller titled Salvation Day, written by Kali Wallace and being published by Penguin Random House's Berkley Books on July 9, aims to break out of the pack with its riveting pace and terrifying space-based hostage plot.

The storyline is set 400 years in the future, after a terrorist cell drops atomic bombs from an orbital weapons platform into the Earth's atmosphere. In the aftermath, the planet heals and reforms under a paranoid totalitarian government. A cultist faction led by a rebellious girl named Zahra kidnaps a group of graduate students and holds them hostage aboard the House of Wisdom, a massive research and exploration vessel long abandoned by the government of Earth. Ten years earlier, the notorious spaceship was the site of a viral outbreak that killed everyone on board.

Zahra and her crew are unaware of what lurks on the ship — a devastating secret buried by the global government. This shocking threat to humanity lies sleeping alongside the drifting corpses, until Zahra's extremists awaken it.

SYFY WIRE spoke with Wallace (Shallow Graves, City of Islands) regarding this unrelenting sci-fi mystery, the genesis of her inspirations, and what readers can expect from the book's turbulent outer-space plot.

After the chat, strap in for an exclusive chapter excerpt from Salvation Day!

Credit: Berkley Books

Where did the novel's concept spring from, and what were your inspirations?

The novel began, strangely enough, with the setting. I became enamored with the idea of writing something set aboard a long-abandoned spaceship, a craft almost Gothic in feel, where something terrible had happened in the past. I wanted to capture the deeply unsettling feel of entering a dark, dangerous crypt in space, and to explore all the fears and mysteries that went along with that.

When I started to dig into the details of the story that could fit into that horrible place, I realized I kept going back to Alien and Aliens — the prime pop culture specimens of Bad Things Happening In Space — and thinking about how those movies made me feel: the first with its slow build and agonizing tension that erupts into violence at precisely the right moment, the second with its non-stop action and flawless pace that leaves you breathless. People always say if you're going to steal, steal from the best.

Later on, when I was developing the world more deeply, I was inspired quite a lot by the depth and breadth of world-building in James S.A. Corey's Expanse novels, which show a future for humankind in which people remain people, full of flaws and prejudices, even as the universe around them changes in ways they never expected.

Credit: Orbit Books

Can you take us on a quick tour of the narrative and its overarching themes?

Salvation Day is the story of a young woman named Zahra who leads a small group of people to attempt to seize control of an abandoned spaceship called House of Wisdom. The ship has been orbiting Earth for ten years, ever since a viral outbreak killed nearly everybody on board. There was only one survivor, Jaswinder, who was a child at the time. Zahra and her group abduct Jaswinder to break through the quarantine that has been enforced around the ship since the outbreak.

Suffice it to say that once the two groups — the abductors and their victims — are aboard the ship, things begin to go wrong, then things begin to go very wrong. It turns out the government has been hiding the truth of what happened aboard House of Wisdom, and now a bunch people have stumbled unknowing into the scene of a horrific tragedy they never understood — and it won't take long for them to realize the cause of the tragedy is still there, still dangerous beyond anything they're prepared to handle.

My goal was to write a fast-paced, action-packed thriller with powerful characters and genuine horror elements, but also to explore some bigger ideas while putting my characters through the wringer. I want to ask questions about what happens when a supposedly enlightened society marginalizes its most vulnerable members, what happens when governments foolishly keep dangerous secrets for self-protection, and how the traumas of the past carry on as wounds inflicted upon younger generations.

What sort of research process did you undertake, and did you learn any startling facts?

I have a Ph.D. in geophysics, so when it comes to the hard science aspects of writing science fiction, I often know just enough to know what I don't know, and I can wing it from there.

But a lot of my research was in another realm entirely: cults and how they form. The group Zahra belongs to is functionally a cult, and I wanted to write the perspective of a cult member as well as I could. I spent a lot of time reading, watching documentaries, and listening to podcasts about various real-world cults: the People's Temple, the Manson family, Heaven's Gate, Rajneeshpuram, Aum Shinrikyo, etc.

One of the works I found most fascinating and helpful was Seductive Poison, the biography of Jonestown survivor Deborah Layton, who is honest and clear-eyed about why she joined the People's Temple, what it provided to her that was missing from her life, and how the people at Jonestown were driven into despair.

The most interesting thing I learned is that while pop culture loves to portray cult leaders as brilliant, alluring men (and women) with almost supernatural powers over their followers, they are petty, cruel, self-centered people whose power and reach is always limited by their own delusions, substance abuse, and greed.

What's the most frightening thing you discovered about space travel?

To me, the most terrifying thing about space is how freaking big it is. I don't think humans have any instinct for comprehending scales that big, so when I try to think about it, about how far space travelers are from help should anything go wrong, I find it overwhelming. There are places on Earth that are dangerous to explore because of how unreachable they are, but it's nothing compared to the vast distances of space.

Has there been any interest in Salvation Day by Hollywood producers?

There has! I can't share the specifics yet, but Salvation Day has been optioned by a production company for a feature film. When I can provide more details, you better believe I will be shouting it from the rooftops.

What do you hope readers take away and absorb from your sci-fi thriller?

What I most hope readers get from Salvation Day is a wild ride that captures their imaginations and gives them some combination of heartache and thrills, but I also hope it gently nudges them to think about the choices humans make, how those choices are represented in the governments we build, and what kind of future it is we're racing toward in the world we have right now.

Now enjoy our exclusive chapter excerpt from Salvation Day by Kali Wallace and published by Berkley Books.

From Chapter 3 – "Zahra"

Beyond the hatch was a sea of stars.

I blinked, turned my head, moved my light. The stars winked and turned. It was not empty space, but a cavernous chamber filled with the tiny, glinting reflections. One of the tiny stars floated close. I reached. It bumped against my glove and spun away, so I stretched farther and caught it.

It was a shard of glass. Thinner than my finger, clear as crystal.

All of those glinting lights, they were broken pieces of glass floating in the chamber. By opening the door, we had set them turning and glinting, a strange and beautiful dance of air currents and debris. I looked around until I spotted large panes of glass secured to one wall, the whole stack of them shattered where something heavy had struck it in the center. Throughout the cargo bay there were crates and boxes floating free, broken away from the nets and bands meant to hold them in place.

I let go of the shard and sent it spinning back into the darkness. I tracked its motion through the cargo bay. The beam from my headlamp danced over the walls, found conduits and panels, cargo secured to the wall with webbing, and a pair of legs.

I let out a startled yelp and release my grip on the handle, then grabbed for it when I realized I wasn't anchored to anything. My body continued to turn, and I wrenched my shoulder trying to stop myself. I kicked at the wall to straighten my arm and caught my feet against the edge of the open hatch.

Malachi's voice came over the radio: "Zahra? What's going on?"

I took a steadying breath, then another. Dag was still in the airlock, his light shining directly at me. Even without seeing his face I knew his expression would be one of stolid disapproval; I should have let him clear the cargo bay before entering.

Carefully, carefully, I turned to look at the wall above the hatch.

"I'm fine." My voice was shaky, so I said it again, more firmly. "I'm fine. I was startled."

"By what?" Malachi asked.

"I'm not sure," I said.

It was a lie. I knew what I had seen.

Boots. Legs. There was somebody above me.

I had thought I was ready for them, the dead who waited for us.

Four hundred and seventy-seven people had died aboard House of Wisdom. When I had tried to imagine them, I had seen a medical bay filled to capacity, body bags bundled in neat stacks, storage rooms turned to morgues, faces hidden behind white sheets. I had dreamed about walking through gleaming clean corridors, and all around me there had been silent figures wrapped in white, with no features except indistinct shadows where their eyes should be. In my dream, I had reached out to them, to tell them they didn't have to stay aboard the ship anymore, but every one had turned away.

I told no one of the dream. Fear, Adam often said, was more deadly than a virus. We had always known we would have to dispose of the dead to make House of Wisdom our home. Panya was planning a ceremony, something mournful and respectful, to prove to the people of Earth that we were not callous criminals.

I pulled myself along the wall, using a line of cargo clamps as a ladder. I was not going to flinch away. We had learned everything we could about the Zeffir-1 virus. We were vaccinated, we were trained, and we had come prepared with supplies for testing the air, cleansing the filtration system, detecting any active traces of the virus that lingered. The Pre-Collapse warlords who created Zeffir-1 had designed it to kill quickly then spontaneously denature: cruelty and cowardly stealth had been their goals. My mind was filled with knowledge about that hateful weapon.

"What is it?" Dag said.

His light grew brighter behind me as he came through the doorway, giving me an overlarge, distorted shadow. I climbed over the crates until I could see the corpse.

She had not finishing putting her spacesuit on. She wore no helmet, no gloves, and the legs weren't properly sealed into the boots. Her face was waxy and shriveled. It had been cold and dry inside the ship for ten years. She had been mummified. Her straight brown hair floated like a fan around her face.

Her entire torso, her shoulders, her upper arms, they were all stained with blood.

It was such a shocking sight I thought at first my eyes were deceiving me. It could not be blood. It had to be something else -- oil, paint, my mind tripped over the unlikely possibilities. The stains were so dark, the blood so thick. I could not immediately locate her wounds. I had to be wrong. I needed to get closer. I could not make myself move.

A rapid and totally fatal outbreak of Zeffir-1. A known weaponized virus, a savage artifact from humanity's dark past, set upon the ship by a known monster. That was what they had said. Dizziness, fainting, fatigue, internal bleeding that might lead to a bloody nose or bloodshot eyes or massive bruises, but nothing like this. Rapid pulmonary failure. An hour, maybe two, from the onset of symptoms to death, after two days of incubation within the body. Within minutes the victims were too weak to move, much less save themselves. Many fell into comas almost immediately and would not have suffered. That was how House of Wisdom was lost. For ten years SPEC had been telling the same story.

This woman had not died in a coma. She had not died quietly.