Subtitled "a fable," the novel follows Adi, a former schoolteacher, amateur jazz clarinetist, and grieving father, as he takes on a five-week solo mission to eradicate invasive goats from Santa Flora, a remote, uninhabited Pacific island. What begins as a conservation assignment becomes a moral reckoning with the boundaries between killing and saving, cruelty and compassion.
Before dawn, Adi boards a naval boat with his gear, including a padlocked rifle case. The captain identifies Adi as a "killer" rather than a scientist, a label Adi neither confirms nor denies. When asked if there is a "Mrs. Killer," Adi lowers his eyes, revealing only absence. The captain shrugs: "Killers kill," just as "sailors sail." At Eremos Cove, the mate ferries Adi ashore to a primitive sealers' hut and studies the rifle case, quietly asking if Adi really gets to kill them all.
A flashback reveals how Adi was hired. At a conservation foundation in the capital, an interviewer explains that feral goats, left by nineteenth-century whalers as a living meat supply, have devoured Santa Flora's native cloud forest, driving multiple endemic species to extinction, including the Santa Flora Reed Warbler and 32 plant species. Two to four thousand goats remain, and the only solution is to shoot every one. When the interviewer asks if Adi has children, he replies, "I did" (22), silencing her and revealing unspecified loss. Asked about firearms experience, he admits only "a bit," concealing total inexperience, and she hires him.
The hut is cramped, furnished with rope-frame beds and a framed portrait of a stern old woman in pince-nez glasses whose frown becomes a recurring presence. Adi unpacks provisions and the rifle, a .308 bolt-action with a scope. On the beach, he fires at the open ocean for the first time; the recoil slams the scope into his forehead, opening a gash. He turns from the watching goats, not wanting them to know he has never fired a gun.
Insomnia afflicts him; the island's silence makes life feel "unalive." At dawn, seven nanny goats stand near the hut, staring with horizontally slitted eyes. He raises the rifle twice but cannot shoot. He fires skyward to scatter them and chases them into a mangrove thicket, where he finds a small bird with a broken wing. He identifies it as the Santa Flora Reed Warbler, last documented in 1983 and believed extinct, driven to extinction by the goats. He names the bird E3 and vows to make things right.
On his first hunt, Adi finds a Teenage Mutant Ninja Turtle action figure in coastal debris resembling one his dead son, Jairo, loved. Inland, he stalks a lone goat; the second of two shots hits its heart by luck. Standing over the dead nanny, he whispers an apology. He hoists the carcass homeward, but the weight forces him to butcher it with his machete, sobbing. He drags only a rear leg back to camp, roasts it, and eats while crying.
He minces scraps for E3, which devours them. Heading out again, he finds reasons to spare every goat he encounters; the randomness of who lives and dies triggers thoughts of Jairo. Shortly after, he shoots a solitary billy goat. That night he devises a new plan: eradicate only males. Without billies, no kids will be born, and the nannies can live out their days as the island regenerates.
On a reconnaissance hike, Adi descends into a valley where a remnant cloud forest survives, a lush pocket representing the green heart of what Santa Flora once was. Continuing north to Campo Langosta, the island's other anchorage, he stumbles at midnight into two illegal shark finners. Grejo, lean and tattooed head to toe with sea creatures, holds a pistol. His partner, Chuky, is pockmarked and big-bellied. Over
aguardiente, a rough cane liquor, Grejo challenges the eradication, insisting nature does not care, and accuses the government of hypocrisy for paying Adi to kill while criminalizing shark finners. He aims the pistol at Adi's forehead, then lowers it.
Adi slips away once both men pass out. Back at the hut, the seven nanny goats show increasing familiarity, following him and watching him swim. He names them; Harmony, a charcoal-splotched goat with a bandit mask, becomes the most distinctive. Using a dead billy's horn, Adi fashions a crude wind instrument and plays jazz standards. Harmony bleats along almost in key, triggering Adi's first smile on the island, an echo of playing clarinet over Jairo's crib 11 years before. Jairo, diagnosed at 18 months with a neurological condition involving cognitive rigidity, shared a Sunday ritual with Adi of folding and flying paper airplanes.
When E3's meat supply runs low, Adi heads out to hunt but first witnesses the shark finners haul a live shark onto a ramp, slice off its fins, and kick the still-living animal back into the sea. When Grejo spots him and waves casually, the gesture claims Adi as a fellow killer. Still shaken, Adi encounters a large billy on a ridgeline but cannot focus: Through the scope he sees the sinking shark, Harmony singing, Grejo waving. Distracted, he fires and wounds the billy in the rear leg. The goat lurches away. Adi follows its blood trail for hours but loses it in a dark gorge. He resolves to return at dawn, end the billy's suffering, and then quit: The goats are not to blame; their only crime was to keep growing where humans planted them.
Stumbling back to the hut, he discovers that Oliver, a rat he had befriended, has killed E3. Only feathers remain in the box. By leaving the cover off in his rush, Adi has caused the final extinction of the Santa Flora Reed Warbler.
Adi lies sleepless beside the empty box. The portrait of the stern old woman seems to whisper: "Killers kill." At dawn he plays his horn, but Harmony declines to sing. He sets out to find the wounded billy, but rain has washed the blood trail clean. Standing at the spot, he catalogues his failures: the island, the bird, the goat, his son, his marriage, himself.
Gunshots jolt him. Through the scope, he sees Grejo and Chuky below nearby cliffs, drunk and shooting at four goats stranded on a narrow ledge. Adi fires skyward, rupturing his own eardrum. The men wave, gesturing for him to join. The scene triggers the full memory of Jairo's death: Jairo, 11 and neurodivergent, sneaked to the apartment rooftop to test a paper airplane. Two older boys from the building, Yorly and Ronny, were there. They told police Jairo jumped, but a witness saw the boys' faces appear over the ledge only after Jairo fell. Adi believes they dared Jairo to fly, exploiting his trusting nature. Two days later, Adi's wife, Deyanira, brought home a gun from her crime-boss grandfather and begged Adi to kill the boys. He refused, insisting he was not a killer. She left the next day.
On the cliff, the finners' shots draw closer. A goat nearly falls. Through the scope, Grejo fires, misses, drinks, and waves, daring Adi to participate, daring him to fly. In that moment, Adi understands what saving Santa Flora truly requires: He must stop these men from destroying what remains. He drops to a knee, steadies the rifle, pins the crosshairs to Chuky's chest, and fires. Chuky lurches backward. Grejo stares up in bewilderment. Adi chambers another round and, without a single question in his mind, fires again.