Jarvis Tanner runs a plant-boosting operation using steroids, but the runoff from his setup mutates the local ticks, turning a quiet region into a dangerous landscape of hidden threats. In response, Tyler Burns is sent to join a wilderness project meant to help him face his fear of the woods, where he soon crosses paths with campers Darrel “Panic” Lumley and Kelly Mishimoto. Their journey begins with a routine supply stop, a moment that quickly spirals as tensions rise in the group.
At a store, Melissa is confronted by Sir and Jerry; while Sir admonishes Jerry to back off, the moment marks the beginning of a relentless escalation. Tragedy strikes when Jarvis’ hamster is killed by a tick, and Jarvis himself is attacked before a snare traps him, causing eggs to rain down. The caravan finally reaches the campsite, where Tyler and Rome stumble upon an egg and decide to destroy it, hoping to curb the threat before it spreads. Yet the danger intensifies: Melissa is clawed by a tick, and Tyler fights it off, even as the creatures continue to close in.
The situation deteriorates further when Panic’s dog Brutus is mauled and killed by another tick, prompting Panic to withdraw from the camp. In a harsh turn of events, Tyler ferries Brutus’ body to a veterinarian, who discovers a tick hidden inside Brutus. The tick becomes a minute menace that scurries around the room until the vet kills it. Panic himself is attacked, his struggle with the tick leaving most of it clinging to him as the head burrows inside. The tension peaks as Kelly and Melissa uncover Sheriff Parker’s corpse, while Didi eventually finds Jarvis, who has amputated his legs and harbors ticks burrowed inside him. A new trap ensnares Jarvis, and his face erupts in a grotesque explosion that underscores the nightmarish turn of events.
From there, Panic stumbles onto Sir and Jerry’s farm, and tragedy compounds when Sir shoots Panic, inadvertently igniting a tank that bursts into flames. Seeking shelter, the survivors take refuge in a cabin as fire closes in. Inside, Charles lets Sir and Jerry in, but Panic reappears nearby and reveals that he was shot by Sir before dying. The chaos continues as Sir shoots Charles in the leg while Jerry attempts to seize the van. A tick finishes Jerry, causing the vehicle to crash into the cabin. Another tick crawls out from Panic’s corpse and rips into Sir, while Tyler drives the van through a window to gain an escape route. The desperate group sets the fleeing vehicle aflame and drives back toward civilization, only to discover an egg mysteriously dropping from beneath the van as they race away, a grim reminder that the danger may not be finished. Rome is left to contend with the bite of a lingering tick en route to safety, and the final image hints that the threat may have survived the journey back to the outside world.
