In a dense forest on a remote island, a team of loggers led by Mac faces stiff opposition from protesters led by Rita, a known eco-terrorist. The company employing them is conducting an experiment in the area, overseen by Carter, a chemist. When a logger is struck by a spike on a tree, he sustains a wound and the sap from the tree seeps in, triggering a shocking transformation that begins to change him.
The president of the company, Anderson, decides to send his son Tyler to investigate the loss of contact with the loggers, hoping to uncover the truth behind the disturbance. Tyler arrives to find that most of the loggers and protesters have become zombies. He discovers a bunker where Mac, Rita, and Carter have taken shelter, along with other survivors including Luke. The company’s lab team soon learns of the outbreak when a chemist examining one of Carter’s samples is infected by the altered sap, signaling a wider crisis.
The board overrules evacuation plans, and Tyler’s father wishes to rescue his son but is blocked, as the board orders a quarantine instead. The survivors stagger to escape, leaving the bunker only to find the road blocked by the company’s men. They are scattered, and more people fall to the zombie threat. Reunited later at the logging base, Mac retrieves another truck and the group resolves to head for an abandoned facility to radio for help, though the camp’s radio appears dead.
Amid the chaos, Tyler and Rita grow closer, while Luke is dragged away by the undead as Carter becomes paralyzed by fear and fails to intervene. Carter’s confession follows: the company had him conducting genetic experiments to grow the trees faster, a revelation that explains the deadly profits behind the operation.
The next day, they push toward a new exit but encounter more zombies. Mac, overwhelmed by grief and doubt after seeing Luke as a zombie, kills Luke with an axe, and Rita offers a quiet, comforting presence. A helicopter hums in the distance, but instead of deliverance, gunfire erupts as the craft opens fire. A renegade band of surviving loggers appears, rescuing them and revealing the company’s plan to wipe them all out.
Inside the camp, a militaristic regime governs a cruel game: a chosen member must kill a certain number of zombies in a pen. That night, the head of the camp tries to assault Rita, but Tyler intervenes to defend her. The two acknowledge their growing attraction and share a night of intimacy.
The following day, Carter is selected to enter the pen, but he freezes, jams his gun, and needs rescue. The other loggers torment him for his fear, deepening his sense of isolation. Broken in spirit, Carter slips away from the camp with an axe, and that night, zombies wander through the open gate, slaughtering many. Mac, Rita, and Tyler survive long enough to wake and flee; Mac is bitten at the gate.
Rita admits to Mac that she was the one who spiked the tree, and in his final moments as a human, he forgives her. As they run, Carter’s screams echo in the night; Tyler attempts a rescue, but the pair are overrun by the undead. Rita, now the last survivor, spots the lights of a road and follows it in a bid for escape.
In the end, back at his mansion, Tyler’s father sits with a heavy heart, understanding that his decisions contributed to the loss of his son. Across the landscape, Rita presses onward, hoping to find a way off the island as danger—and the memory of what was done—lingers.
