Mercenary Martin David (Willem Dafoe) is contracted by the military biotech company Red Leaf, tasked with a rather grim mission to travel to Tasmania. His objective is to gather samples from the elusive Tasmanian tiger, and with orders to eliminate any remaining tigers to prevent rival organizations from accessing their DNA. The partnership involving this operation is orchestrated through a middleman named Jacek Koman. The Tasmanian tiger, believed to be extinct, represents one of the most unique and limited creatures on the planet, making its detection crucial. With Red Leaf citing two recent confirmed sightings, pressure mounts on Martin to finalize his assignment within a few weeks.
Martin is an expert in meticulous planning and exhibits a disciplined demeanor throughout his work. He lands in Hobart, presenting himself as a university biologist to integrate into the local environment. Settling in with the Armstrong family, consisting of Lucy (Frances O'Connor) and her two young children, Katie (Morgana Davies) and Jamie (Finn Woodlock), becomes his temporary home, albeit under difficult conditions. The house is frequently without electricity, relying on a malfunctioning generator, and the water supply is questionable at best. After being unable to secure accommodations at the local tavern, Martin must accept the uncertainty of staying with the Armstrongs.
Lucy, who is notably lethargic due to prescribed medications she takes following the mysterious disappearance of her environmentalist husband, Jarrah Armstrong (Marc Watson-Paul), spends much of her time asleep. The town's suspicions linger regarding her husband’s disappearance, especially amidst ongoing tensions between local loggers seeking jobs and environmentalists, referred to as 'greenies', who advocate for forest protection.
As Martin attempts to adapt to his surroundings, he finds himself at odds with the community, who suspect him to be another environmentalist like Jarrah. Amidst uncomfortable living conditions, he takes it upon himself to make improvements around the house, such as fixing the generator and even the bathtub. His excursions into the Tasmanian bush, which span over twelve days, involve setting strategic traps while patiently waiting for the tiger to appear. With the rugged land serving as both home and hunting ground, Martin keeps track of his traps meticulously marked on his map.
During his time in the wilderness, Martin hears distant gunshots, indicating potential threats from local hunters or perhaps even rival operatives. Upon returning to the Armstrong residence for supplies, he develops a bond with the children and uncovers that Lucy’s medications are supplied by Jack Mindy (Sam Neill), who has been unofficially looking after the family. Recognizing the detrimental impact of Lucy's drug dependency, Martin makes the drastic decision to confiscate her medication and assists in her recovery when she is unconscious.
After a period of recovery for Lucy, Jamie provides Martin with critical information—a drawing that suggests the tiger's habitat near small bodies of water and trees, leading Martin to refine the locations on his map. During subsequent expeditions, he finds evidence of another hunter operating in the area, including an automated camera, but discovers the memory card offers little useful information.
In a shocking twist, Martin uncovers the skeletal remains of Jarrah, shot through the head. Though he honors Jarrah with a proper burial, he keeps this discovery from the Armstrong family. Upon returning, Lucy reveals that Red Leaf had originally hired her husband to locate the tiger, which he shifted away from, choosing to protect wildlife instead. Additionally, she shares that Red Leaf suspected the tiger possessed a paralyzing venom in its bite, which illuminates the stakes involved.
As Martin continues to check his traps, he faces an unexpected ambush from a rival operative sent by Red Leaf, who has been tracking Martin’s movements based on maps left behind at the Armstrong home. What follows is a tense confrontation where Martin cleverly leads the rival operative into one of his traps, allowing him to regain control and eliminate the threat.
Upon returning to the Armstrong home, which he finds burned down, he learns a tragic truth from Mindy: Lucy and Katie perished in the accidental fire, while only Jamie survived and was taken into custody by authorities. Consumed by grief and guilt, Martin resolves to go deeper into the bush for one final search, determined to find the Tasmanian tiger and put an end to Red Leaf's ambitions.
Eventually, he does locate the creature but grapples with the moral weight of his task and ultimately decides to take its life. He cremains the body, erasing any evidence of the tiger’s existence, and informs Red Leaf that their pursuit is "gone forever." The narrative culminates in an emotional reunion at a school where Jamie, who remains isolated, excitedly runs toward Martin, and the two embrace, reflecting a bittersweet resolution amidst the chaos that has unfolded.
