Over the 48 bells before departure, Sasha observes the unit’s individual routines. Tristian barely leaves the Exploratory Room, while Patrick spends both nights gripping his cross, and Ingrid visits her sister, Bretta, in the Kitchens. Damien rests his injured ankle, and Rumi meditates.

Levi escorts Sasha to her training with her former mentor Dr. Kumar, who launches into an intensive crash course. When Sasha insists on donating blood for Damien before the mission, Kumar limits how much she can give. Knowing that Kumar was the one to give her the nickname “Death’s Angel,” Sasha asks him why, and Kumar reveals that he never meant it as a reference to her immunity; he gave her the name out of his admiration for her habit of staying with dying patients so that they wouldn’t be alone.

Levi then takes Sasha to be fitted in her radiation suit: a full-body gray metal exoskeleton with a helmet offering night vision, navigation, partner communication, and oxygen monitoring. She finds it deeply claustrophobic. When she admits to being unsure whether anything is worth saving, Levi reassures her that something always is.

On the morning of the mission, Ingrid slips out early to visit Bretta in the Kitchens. When Sasha asks Isla why she joined the Force, she answers that it was for the sake of a romance that she then ruined; she stays because she believes in second chances. Levi arrives with coffee that he obtained through a Unit Three contact, reserving an extra cup for Sasha because she’s the only one who thanks him. Patrick delivers a weather and radiation update as the group prepares to move out.

Fully suited, the unit walks toward Haven’s exit. A discussion of call signs breaks the tension as they joke about a Unit Twelve member whose call sign, “SPLAT,” stands for “Shits Pants Loudly and Thunderously” (154). At the guard shack, Sasha spots Jaxon on duty—visibly furious but silent. The unit enters the steel decontamination chamber and seals their helmets. The guards wish them luck and ask them to watch for Units Twelve and Five on the return journey.

Patrick runs a gear check over the helmet communication system, covering radiation suits, weapons, the med bag, navigation, night vision, oxygen levels, and partner channels. When Sasha’s private channel opens, Levi wryly tells her that this is her last chance to run. She refuses.

As Haven’s inner door seals behind the unit, Sasha has a flashback to the last time she saw this entrance. Then, she was sprinting toward it with the dying Lara in her arms. Lara urged Sasha to go on without her and professed to be ready to die and join their family.

In the present, the outer doors begin to grind apart. Bright light spills in around Tristian’s silhouette as he faces his unit, and they recite the unit’s oath: “As long as there’s life, we defend it with our own” (158).

Upon stepping onto the surface for the first time in nearly six years, Sasha is confronted by a vast, gray, lifeless expanse of crumbling buildings. On the private partner-only radio channel, she tells Levi that the world stopped existing for her when her family died. As Haven’s doors seal shut, she cries. On the edge of town, Rumi stops at a nondescript building and places a stone alongside a long row of others. Patrick wraps an arm around her as the unit continues.

Later, the unit encounters Unit Twelve returning. Their commander, Henderson, warns Tristian that Kaleo left Outpost Two in poor condition and is unlikely to share useful intelligence; Henderson wants to speak about Sasha and Kaleo when Tristian returns. As Unit Twelve passes, Henderson calls Damien by his surname.

Damien explains their mission tradition to Sasha, in which each member poses one question that everyone must answer honestly or else take second watch. Isla reveals the unit’s call signs; Rumi is “Eagle,” Isla is “Sunshine,” Damien is “Buddy,” Ingrid is “Medusa,” Patrick is “McFumbles,” and Levi is “Raven.” Tristian is “Hades” due to his high body count in the war. Sasha has no call sign yet but will earn one by the end of the mission. Damien poses his question, asking what everyone would eat if they could have anything. Each answer is tied to personal memory. Damien ultimately admits that what he really misses are his grandmother’s weekly family dinners. The confession settles heavily over the group.

At Outpost One (an underground shelter with cots, a kitchen, and a shower), Damien removes Unit Five’s posted flag in protest against Kaleo’s callous actions in the past; Tristian orders it replaced, so Damien puts it back upside down. That night, Rumi asks the unit members to name their greatest regret. Ingrid says “fear” and clarifies “always letting it win” (173). Levi’s regret is not forgiving people while they were still alive. Rumi regrets allowing her group to split up and failing to be present when they died. Sasha and Tristian decline to answer the question.

On the third day, the unit reaches Outpost Three, which is far more primitive than the others. On the march, the group notes that Kaleo’s unit, Unit Five, has vanished from the navigation system. When Patrick raises the possibility of a mutiny, the heavy silence confirms that the idea isn’t hypothetical. Levi privately tells Sasha that everyone needs a backup plan.

That night, Rumi privately tells Sasha that her grandmother believed that the dead live among the stars to watch over the living. Inside, the unit discovers that Kaleo’s group has taken two blankets from the outpost’s supplies in a deliberate provocation. Damien pushes for retaliation, but Tristian orders him to stand down.

Sasha wakes in the night to find herself curled against Tristian and overhears him and Levi debating over whether they should abandon their radiation suits in the next day’s explorations of the Abyss in order to cover more ground. Tristian mentions the risk of exposure, but Levi argues that the suits’ technology fails out there anyway. He stresses that Haven is out of time, and Tristian agrees. In the dark, Tristian pulls Sasha’s blanket higher. She presses closer to him and sleeps peacefully for the first time in days.

The next morning, Tristian briefs the unit, using a hand-drawn map, and everyone agrees to go without their suits. Pairs are assigned by section: Damien and Isla head to the south, Rumi and Patrick go to the north, Tristian and Ingrid go to the far west, and Sasha and Levi go to the nearest eastern section. As the sole medic, Sasha objects to the split, but Tristian overrules her. Before departure, she quietly re-wraps Damien’s badly swollen ankle and gives him anti-inflammatory medication, noting privately that his B-negative blood type means that she’s his only compatible donor—a significant risk if he’s seriously injured.

During the search, Levi tests a known explosive trap to see whether it resets. It does, and Sasha instinctively throws herself over him to protect him. Later, as they walk, Levi describes a fellow soldier who stayed with him through his worst years and became the first real family he ever had; he’s clearly describing Tristian. Levi tells Sasha that her deep anger is really grief over the loss of her entire world; he stresses that acceptance is the only way forward.

On the fourth morning, Ingrid radios that they have found an entrance. Tristian went down alone, but he has gone silent, and the team is concerned that he may have been injured. Overriding Levi’s hesitation, Sasha insists that they go to Tristian’s last known location. As they run, Levi shouts a sudden warning, and a trap fires from the ground, pitching Sasha forward. Levi is caught by the trap and collapses, bleeding heavily.

Sasha radios that Levi is down and then fights her way toward him through the metal stakes. When the trap retracts, she reaches him and realizes that his deltoid is torn to the bone, that his shoulder is dislocated, and that he’s losing a lot of blood. As she applies a tourniquet and pulls him to a safer distance, he loses consciousness.

Drawing on her father’s battlefield training and Kumar’s sessions, Sasha collects a bag of her own blood while simultaneously starting IV fluids in Levi’s arm. She wraps him in her clothing and a tarp and begins dragging him four miles back to Outpost Three, radioing the unit to meet her there. Partway back, she draws a second bag of her own blood, knowing that doing so will push her body close to its limit.

At the outpost, she hoists Levi down the stairs, cleans and packs the wound, and attaches the second blood bag. The bag that she pre-donated with Dr. Kumar is placed inside her heated radiation suit to warm for later use. To fight hypothermia, Sasha wraps herself around Levi beneath every available blanket.

Levi has no radial pulse. His breathing is rapid and shallow. Sasha is dizzy from blood loss, and she can’t rule out the possibility that Levi is bleeding internally. Terrified that she made the wrong call in deciding to go toward Tristian, she holds Levi and tells him to hang on as she waits desperately for the rest of the unit to return.