Mercenary Martin David is tasked by the military biotech firm, Red Leaf, to travel to Tasmania and gather specimens of the allegedly extinct thylacine, also known as the Tasmanian tiger. His mission comes with a dark ulterior motive: to eliminate any remaining tigers to prevent rival organizations from obtaining their DNA. Disguising himself as a university biologist, Martin moves into the home of the Armstrong family, which consists of Lucy and her two young children, Katie and Jamie.
Lucy's state is one of persistent dullness, a consequence of prescription medications she takes after the mysterious disappearance of her environmentalist husband, Jarrah Armstrong. This incident stirs local speculation, especially due to a significant conflict between desperate local loggers and a group of environmental activists, known as "greenies," who are blocking forest access to protect it from deforestation.
During his twelve-day excursions into the wilderness, Martin sets steel traps and makeshift snares, patiently waiting for a glimpse of the elusive tiger. He leaves the Armstrong family a map with his coordinates to ensure they can locate him if he fails to return on time. Throughout his short stays to gather supplies, Martin develops a bond with the children and uncovers that Jack Mindy, a family friend, regularly brings Lucy her medication. Recognizing the damage her dependency causes, Martin eventually confiscates her pills and tends to her while she is unconscious. This act leads to Lucy's recovery from her addiction.
During one of his visits, Jamie provides Martin with a crucial lead about the tiger’s location—a drawing depicting the animal near trees and bodies of water. Following this clue, Martin heads out and inadvertently discovers Jarrah’s skeletal remains, realizing that he was shot in the head. He provides Jarrah with a proper burial but chooses not to share this discovery with the Armstrong family. Upon returning, Lucy informs Martin that Red Leaf initially hired Jarrah to find the tiger, which he abandoned to fight for environmental protection, believing the company's interest in the tiger was due to its potential venomous bite.
As Martin checks his traps, he is ambushed by a replacement operative from Red Leaf who forces him to guide him to the tiger's cave. Cleverly, Martin leads the man past one of his traps where the operative's leg gets caught. In the struggle, Martin manages to free his hands, retrieves a dropped rifle, and kills the operative just before he escapes the trap. During the encounter, he discovers the map he had previously left with the Armstrongs in the operative's possession, realizing that the man has already visited their home.
When Martin returns to the house, he is devastated to find it in ruins. Confronting Mindy, he learns of the tragic fate of Lucy and Katie in a supposed accidental fire while Jamie has been taken into custody. Overcome with grief, Martin resolves to venture back into the wilderness one last time to locate the Tasmanian tiger and eliminate any trace of it that Red Leaf seeks. Eventually, he finds the creature and, in a moment of painful resignation, he shoots it and cremates its remains.
Afterward, Martin returns to town and contacts Red Leaf to falsely inform them that their quarry is "gone forever." He then visits a school where he finds Jamie sitting alone on a bench. Upon spotting Martin, Jamie runs towards him in excitement and they share a heartfelt embrace, signaling a small victory amidst the darkness of their circumstances.
