Beneath

The novel opens with a journal entry dated "Day 100," in which an unnamed narrator reflects on regret and loss. The entry closes with a confession: They would have said "I love you" more.

Six years after a global war reduced the planet's surface to an irradiated wasteland, humanity's remnants shelter underground in Haven, a network of tunnels organized into five sectors: the Kitchens, the Force (a military organization), the Hospital Ward, Sanitation, and Expansion. Each person wears a colored identification band and is assigned a health score that determines access to medical care and sector placement. Sasha Cadell, 23, spent five years in the Hospital Ward, where she earned the nickname "Death's Angel" for her immunity to illness and her habit of sitting with dying patients so they would not die alone. Six months ago, after the death of a Force member named Lily, Sasha transferred to Expansion, seeking the numbness of monotonous labor.

Before the war, Sasha's father, a retired Army Special Forces soldier, trained her in firearms to protect her younger siblings, Lara and Eli, before he left to fight. Her mother gave up in the aftermath. An intruder killed Eli over food, and Lara died before reaching safety. These losses left Sasha consumed by guilt.

Commander Tristian Hayes of Unit Seven, one of the Force's elite Exploratory Units, has spent months petitioning for a medic. Three years earlier, Sasha nursed Tristian back from a near-fatal fever and then spent two years secretly treating Unit Seven members in a hidden closet near the Ward, bypassing the health score system. When Force Commander Burdon approves the transfer, Sasha is drafted against her will. She demonstrates exceptional marksmanship, and Burdon assigns her to Unit Seven as Lily's replacement. Burdon also publicly orders the entire Force to "make the Angel fall."

Unit Seven includes Tristian; his second-in-command, Levi Williams; Patrick McMurphy (operations and weapons); Rumi Sato (engineer); Isla Ford (operations and intel); Ingrid Sorenson (communications and weapons), who was Lily's partner and blames Sasha for Lily's death; and Damien Cruz (communications).

Training pushes Sasha through sparring, an obstacle course, and the House, a holographic combat simulation. During a House exercise, Sasha freezes when she sees a virtual child held captive, reliving the night Eli was murdered. When a Force member attacks her on the mats, acting on Burdon's bounty, the entire unit mobilizes to defend her. Tristian confronts Burdon, secures Sasha's release, and retrieves her confiscated weapons. He then begs Sasha to commit to the unit. She agrees and chooses Levi as her partner, dissolving Tristian and Levi's seven-year bond.

Levi pushes Sasha relentlessly until she climbs a rope she has never completed, a breakthrough signaling her willingness to fight. Tristian reveals the classified truth: Haven's supplies will run out in less than a year. The Exploratory Units' mission is to find a hidden cache of resources in the Abyss, unexplored territory beyond the mapped tunnels. The cache is protected by resetting explosive traps that have killed members of other units, which is why Tristian fought so hard for a medic.

Unit Seven departs for the surface, and Sasha sees the devastated landscape for the first time in six years. Over three days, they trek to Outpost Three at the edge of the Abyss and split into pairs. While searching, Sasha and Levi trigger a trap. Levi pushes Sasha clear but suffers a deep laceration through his right deltoid and internal bleeding from a liver laceration. Sasha stops the hemorrhage, transfuses her own blood, and drags him back to the outpost alone. The unit races back to Haven, and Levi survives with full use of his arm.

Burdon forces Jaxon Taylor, Sasha's former casual partner, into Unit Seven as a replacement. Jaxon reveals that Kaleo, Unit Five's commander, promised him a place in Unit Five if he can get Tristian detained. Meanwhile, Sasha secretly visits Levi in the Ward and swaps their identification bands and health score charts, transferring his severe injury marks onto her own record to protect his standing in the Force. Dr. Kumar, who recognizes the switch, warns her the consequences will be irreversible.

An illness sweeps through Haven, overwhelming the Ward and prompting a mandatory curfew. Ingrid begs Sasha to save her younger sister, Bretta, who has contracted the disease. As Kumar lies dying, he reveals that Lara asked him to watch over Sasha, and he has honored that request ever since. He gives Sasha a small metal chip on a leather cord, telling her a "bird" delivered it with instructions to "keep hope alive." His final words are to "find the snake" and "protect the dead."

Sasha and Tristian's relationship deepens during this period. After learning about Tristian's history, including Burdon's coup that destroyed his first unit, the Angels, and the year Tristian spent as Burdon's lover to gather intelligence, Sasha goes to his room and they sleep together. Tristian later tells Sasha he loves her while she pretends to sleep; she cannot say it back, paralyzed by the fear that everyone she loves dies.

Tristian, Levi, and Rumi execute a mutiny: They falsify radiation readings, jam Haven's doors, and flee to the surface with the full unit. Deep in the Abyss, Sasha inserts Kumar's chip into an indent on a gray metal box. The tunnels come alive, and a massive door opens to reveal rooms of labeled crates containing building supplies, medications, and medical equipment. Tristian radios the unit: "Mission Hope is a success." Before reuniting, Sasha discovers a room of oblong metal pods labeled "Tactical Artificial Biotech Intelligence Tracking Human Algorithm" (TABITHA). When the chip contacts one pod, steam swirls and a woman with gray eyes stares back through the glass, but moments later the pod is empty. She tells only Tristian, who takes the chip and instructs her to keep the discovery secret.

Kaleo arrives with allies, weapons drawn; the cache's activation restores technology across the Abyss, broadcasting their location. Rumi runs to shield Kaleo, revealing a secret two-year relationship. Patrick, her partner and closest friend, is devastated. Kaleo explains that he was never a traitor during Burdon's earlier coup against the Angels. He has spent years as Burdon's lover to gather intelligence, working with Rumi and the late Kumar to deliver the key to Unit Seven. Kaleo leads the group back toward Haven through tunnels dug by the Moles, people in Expansion who have faked their deaths to operate outside Command's control.

Their victory is short-lived. Burdon intercepts them and reveals she has discovered the tampered health score charts. She forces Tristian to become her second-in-command, strips Unit Seven of its Exploratory status, and assigns them to guard duty. Sasha's health score disqualifies her from the Force entirely. Sasha realizes that Henderson, Damien's boyfriend and Unit Twelve's commander whose call sign is "Snake," has been Burdon's unwitting source of information about Unit Seven. Damien trusts Henderson and shares the unit's secrets. Kumar's dying instruction to "find the snake" is a warning about this leak. Rumi meets Sasha's gaze and nods, confirming she has reached the same conclusion.

In the epilogue, Sasha is back in Expansion, swinging a pickax, wearing a gray band. Kaleo, also exiled, sits beside her and mentions "dying," referencing the Moles' practice of faking death to work outside the system. Sasha resolves that she is no longer merely surviving. She intends to live, to fight for the people she loves, and to right what has been broken.