Ariel Sullivan’s Beneath (2026) is a dystopian romance and the second novel in her dueling trilogy that began with Conform (2025). Sullivan is a New York Times best-selling author who grew up in a military family, an experience that informs the novel’s focus on military-style social structures. The novel is set six years after a nuclear war has forced humanity into Haven, an underground bunker with a society that has been organized into a rigid five-sector hierarchy. The story follows Sasha Cadell, a young woman haunted by the loss of her family, who is forcibly recruited from a low-status labor sector into an elite military unit. As she struggles to confront her past, she must join the unit’s desperate mission to find resources before Haven’s supplies run out and everyone perishes.

Set in the same postapocalyptic universe as Conform but 200 years earlier, Beneath functions as a standalone prequel, drawing heavily on dystopian conventions to explore themes of social control and the manipulation of truth. The novel examines The Long-Term Repercussions of Trauma, The Tension Between Individualism and Community, and The Human Tendency to Perpetuate Oppression.

This guide refers to the 2026 Ballantine Books edition.

Content Warning: The source material and guide feature depictions of illness, death, graphic violence, sexual violence and harassment, physical abuse, ableism, substance use, sexual content, and cursing.

Plot Summary

Beneath takes place in Haven, an underground bunker system that serves as humanity’s last refuge after a global war devastated the planet’s surface with nuclear weapons. Survivors have lived underground for six years and are organized into five sectors: the Kitchens, the Force (security and surface exploration), the Hospital Ward, Sanitation, and Expansion (tunnel-digging labor). Each person wears a colored identification band corresponding to their sector, and a health-score system determines access to medical care. Those whose scores drop too low are relegated to lower-class sectors (Expansion and Sanitation) and effectively abandoned.

The novel opens with the narrator, Sasha Cadell, a 23-year-old woman who was 15 when the war began. Now hard-bitten and cynical, Sasha lost her entire family in the war and its aftermath: Her father died fighting; her mother gave up and died of grief; her younger brother, Eli, was murdered by an intruder; and her younger sister, Lara, died of illness upon reaching Haven. Sasha now works in Expansion, swinging a pickax at dirt walls and seeking monotony after years of trauma. Her only diversions come from her periodic trysts with a strutting, cocky Force member named Jaxon, although she has no real affection for him. She previously served in the Hospital Ward, where she earned the nickname “Death’s Angel” for her apparent immunity to illness and her habit of sitting with dying patients so that they wouldn’t die alone.

Sasha’s isolation ends when Tristian Hayes, a Force unit commander whose team’s injuries she often treated, arranges (without her consent) to have her transferred into his unit (Unit Seven) as their medic. Force Commander Lyssa Burdon, who controls the entire Force, reluctantly approves of this plan after Sasha demonstrates her extraordinary marksmanship. Sasha is furious at the transfer and even more furious at her unbidden romantic feelings for Tristian, which she strives to suppress.

The narrative gradually reveals that three years earlier, Sasha sat at a gravely ill Tristian’s bedside in the Ward, urging him to stay alive. He recovered and became the first patient who ever listened to her entreaties. Sasha then spent two years secretly treating Unit Seven’s injuries and protecting their health scores by doctoring their medical records. When a unit member named Lily fell terminally ill and died, the loss shattered the unit. Lily’s partner in the Force, Ingrid Sorenson, tried to attack Sasha, who fled to Expansion and severed all ties with Unit Seven and the Ward.

Now, having been forced to join Unit Seven, Sasha clashes with its members. Ingrid remains hostile, while Patrick McMurphy questions Sasha’s reliability and Levi Williams (Tristian’s second-in-command) grows frustrated with her unwillingness to try her best. Rumi Sato silently watches Sasha’s every move, and Damien Cruz maintains a mask of genial humor. (From her past in the Ward, Sasha knows that Damien is hiding his chronic ankle pain for fear of being removed from the team.) Only Isla Ford remains positive, seeking to befriend Sasha.

As Sasha chafes under Unit Seven’s scrutiny, Burdon publicly targets her, ordering the Force to “[m]ake the Angel fall” (52). Training is brutal. During a holographic combat simulation, a hostage scenario causes Sasha to relive Eli’s murder, and she freezes completely. Over the following weeks, each unit member takes a turn as her bodyguard, and Sasha begins to understand them. When a Force member named Murray attacks her on the mats, she pins him at knifepoint, and Unit Seven mobilizes to defend her, marking the first sign of collective trust.

Sasha chooses Levi as her field partner rather than Tristian, recognizing that her romantic feelings for Tristian would compromise the team in the field. Tristian then reveals classified information: Haven’s supplies will run out in less than a year. Unit Seven’s mission is to find a hidden cache of resources in the Abyss, the unmapped territory beyond the explored area on the surface. These supplies, reputedly left by Haven’s unknown creators, are protected by lethal booby traps. Three Exploratory Units are currently competing to find the supplies; Unit Seven’s most bitter rival is Kaleo, who is now in a relationship with Burdon and openly scorns Tristian and his team. (In the past, Burdon created an unhealthy competition between the three teams in order to punish Tristian after he ceased serving as her second-in-command.)

As Unit Seven departs Haven, Sasha sees the surface for the first time in six years and weeps over the lifeless gray landscape. After several days, the unit reaches the outermost outpost, and at Tristian’s direction, they break off into pairs. Levi and Sasha search the eastern section, triggering explosive traps that suggest something valuable lies beneath. However, when Tristian goes underground alone and then stops responding, Sasha insists that she and Levi redirect to get to him, as he may be injured. During the redirect, Levi triggers a metal spike trap, sustaining a massive laceration, a dislocated shoulder, and internal bleeding. Sasha stabilizes him, drags him miles to the closest outpost, summons the rest of the team, and commands the unit as they all head back toward Haven. They run for days and finally reach safety, taking Levi to the Ward.

In the aftermath, Sasha secretly swaps her identification band and health-score chart with Levi’s, taking on his catastrophic record in order to protect his standing in the Force. Dr. Hari Kumar, her former mentor, discovers the swap but declines to punish her. Burdon then forces Jaxon onto Unit Seven as Levi’s replacement, but as Jaxon eventually reveals, Kaleo has tasked him with destabilizing the unit from within.

A devastating illness sweeps Haven. Sasha secretly treats Ingrid’s younger sister, Bretta. Amid the stress of the crisis, Sasha’s relationship with Tristian deepens. He tells her that he wants her wholly, not just as a distraction, and he refuses to lie about his feelings. Sasha, unable to voice her own feelings for him, watches him walk away but then goes to his room, unable to stay away. They have sex, though she still finds an excuse to pull away afterward.

Levi tells Sasha the history of Tristian’s original unit, the Angels. Four years earlier, Burdon orchestrated an ambush during a mission and then seized command after the previous Force commander died under suspicious circumstances. Tristian returned to Burdon for a year, enduring a relationship with her in order to secretly gather intelligence, but his deception became unsustainable.

Just before Dr. Kumar dies from the illness, he tells Sasha that he has been obeying her sister Lara’s last wish that he watch over Sasha. He gives Sasha a small metal chip on a leather cord, cryptically telling her that a “bird” delivered it with a message to “[u]se it to keep hope alive” (361). His dying instructions are to “[f]ind the snake and protect the dead” (361); he warns that Dr. Uri, the Ward leader, is allied with Burdon.

Sasha barely rejoins Unit Seven in time to participate as Tristian executes a mutiny. Unit Seven breaks out of Haven and heads to the Abyss, exploring the underground tunnels. Sasha and Tristian split away from the others and take the unexplored route. In the tunnels, Sasha finally admits to being afraid of everything: of losing Tristian, of caring, and of being seen. Tristian confesses his own fear but asks to stay by her side. After they have passionate sex in the tunnel, Sasha notices a gray box on the wall and unlocks it with Kumar’s key, activating a door that reveals rooms filled with supplies, medications, and medical equipment. Tristian radios the unit: “Mission Hope is a success” (394). Privately, Sasha discovers mysterious pods labeled “Tactical Artificial Biotech Intelligence Tracking Human Algorithm,” or TABITHA (391). When her blood and the chip make contact with a pod, steam clears to reveal a woman with gray eyes. When Sasha returns later, the pod is empty.

Kaleo, Unit Five’s commander, arrives and reveals that activating the cache also lit up Command’s map, giving Burdon the location of the supplies. He further reveals that Rumi has been his secret partner for two years, gathering intelligence within Unit Seven. Kaleo asserts that he was never truly a traitor during the fall of the Angels; like Tristian, he has been working against Burdon from within. Patrick is devastated by Rumi’s betrayal.

The group reenters Haven through a secret tunnel dug by “Moles,” a covert Expansion crew whose deaths were faked in Ward records. Burdon intercepts them, discovers that Sasha has swapped Levi’s chart with her own, and delivers harsh punishment, declaring that Sasha’s current health score (really Levi’s) disqualifies her from the Force. Burdon then forces Tristian to become her second-in-command, ripping him away from Unit Seven and demoting the unit to guard shack duty, where they will be barred from any future surface missions. Tristian names Levi the new Unit Seven commander and leaves without another word.

Sasha realizes that Kumar’s dying instructions form a coherent warning. “Find the snake” refers to Noah Henderson, Unit Twelve’s commander and Damien’s boyfriend; Henderson’s call sign is “Snake.” Damien has been using his relationship with Damien to infiltrate Unit Seven and pass intelligence to Burdon. The phrase “Protect the dead” refers to the Moles.

In the Epilogue, Sasha has returned to Expansion. Kaleo, also exiled to Expansion, works beside her and hints that they might be able to fake their deaths and join the Moles. Sasha resolves that she will no longer seek merely to survive; she intends to truly live and fight for the people she loves. At this point in the narrative, the supplies have been found but not yet delivered. Unit Seven is fractured but not destroyed, and the woman in the pod remains a mystery.