At Universal Bio Tech Research Facility, scientists push horned vipers further by enhancing their venom with a compound called C12 in the quest to cure disease. The early results look promising when the enhanced venom seemingly cures a woman of breast cancer; however, the same venom proves deadly, and the snakes murder four people. Aided by his own men, Staffin and his security detail subdue the staff to steal the snakes. In the ensuing chaos, the vipers are released and kill everyone except Staffin, who escapes. The snakes then rapidly repopulate, leaving the island in a state of eerie, creeping danger.
On the island of Eden Cove, a couple is murdered on a beach, setting a grim tone. Meanwhile, Cal Taylor visits Doc Jim Silverton for medical insight as the situation outside the facility escalates. Sheriff Hendricks is tipped off that trouble is brewing when Maggie Maggie Martin — a teenager with a secret marijuana cultivation — is suspected of breaking into a store to smoke marihuana. Doc and Cal head to the store’s hidden marihuana garden, trying to make sense of the odd cluster of events and the mysterious link to the vipers.
Outside, a viper bites Jake Willis, a child whose life depends on timely intervention. At a nearby clinic, Cal administers an antivenom, stabilizing him and buying precious time. The shop owner, Nicky Swift, is imprisoned for growing marihuana, a detail that deepens the tension between the investigators and the local community. Meanwhile, Dr. Vera Collins, a researcher from Universal Bio Tech, insists on examining Jake’s bite to determine whether it came from one of their vipers, a request that sets off a chain of high-stakes decisions. Burton, the company’s CEO, introduces Staffin as his security chief and sends his team out with Vera, tightening the control around the unfolding crisis.
Back at the inn, Maggie’s father Jack Martin shares a private moment with a woman named Georgie, but the night turns violent as the vipers strike. Georgie is killed, a brutal reminder of the danger lurking around every corner. Using tools Cal unintentionally left behind, Nicky manages to escape prison and slips into the inn, where Cal helps fend off a viper attack and pulls her to safety. The tension spikes as the vipers begin to close in, forcing a rapid cascade of evasive maneuvers.
As the danger grows, Sheriff Hendricks orders everyone to flee toward the inn, but Maggie makes a wrong turn, complicating the escape plan. The snakes descend on the lobby, and Cal wards them off with a fire extinguisher, buying the others a fragile moment of safety. Jack’s estranged wife Ellie Martin leaves to search for Maggie, her daughter, and she quickly finds herself surrounded by danger. Tom Hendricks, the Sheriff, makes a stand to protect Maggie, locking her in a safe room in his office, but the snakes overwhelm the defenses and Tom is killed in the onslaught. Jack races to rescue Ellie, and they manage to regroup, but the couple remains under constant threat.
The group is eventually forced to retreat to a non-functioning van, where Cal and Nicky tend to the wounded and keep the snakes at bay with improvised defenses. Cal is bitten, raising the stakes even higher. They sneak into a nearby café in search of sanctuary, but Ellie is killed during the chaos, a devastating blow that echoes through the shrinking band of survivors. With ice and makeshift barriers, the survivors barricade themselves inside, discovering that the cold slows the vipers’ advance and buying precious time to plan their next move.
Doc, Staffin, and Vera chart a desperate counterattack, deploying grenades of C12 to subdue the snakes and buying crucial breathing room. One of Burton’s men falls to the attack, a reminder of the deadly costs of the high-stakes plan. Jack gathers Maggie, Nicky, and Cal and escorts them toward the inn, hoping the refuge will hold. The townspeople band together inside the inn as a tense standoff with the snakes unfolds, while those outside scramble toward a boat left by the visitors’ vessel.
The tension peaks as Lewison, a townsperson, reveals that Staffin’s mission was not a rescue but a capture operation — a grim twist that reframes everything the group has done. An aircraft is due at dawn to gas Eden, a plan that could wipe out everyone still on the island. The survivors improvise one last, desperate response: Lewison drives a truck toward safety while Cal, Staffin, Nicky, Vera, and Brownie draw the snakes away from the boat with heat sources and steer them toward a greenhouse. Doc and the rest of the townspeople head for the boat, while Ellie’s grief-stricken family fights to stay alive.
Maggie makes a break for safety, but Doc cannot chase after her and must depart with the rest of the group. Lewison is bitten, and Maggie uses C12 to momentarily subdue the snakes long enough to save Cal’s life. As the situation spirals, Staffin is bitten and dies, and it becomes clear that he had a radio on him the entire time, revealing his plan to abandon the others. Vera’s radio plea to Burton to call off the attack goes unanswered, and Brownie falls to the relentless assault of the vipers.
In a final act of defiance, Nicky and Vera ignite the greenhouse with flares and propane tanks, triggering a massive explosion that buys the team time. The aircraft eventually arrives, but Doc manages to reach them and convinces the operators to spare the island from being gassed. Burton is arrested after Cal records an incriminating conversation in which Vera admits his plan to kill everyone. The uneasy balance of justice is tested when Burton is later released on bail, only to be killed by a snake that has stowed away in his car, a grim reminder that the danger lingers even after the immediate crisis is resolved.
This tense, survival-focused thriller tracks a town fighting an engineered predator while navigating lab ethics, corporate conspiracy, and the costs of heroism in the face of a seemingly unstoppable threat. The cast’s intertwined fates—Nicky, Cal, Maggie, Jack, Ellie, Vera, Burton, and Lewison—underscore a world where every decision can mean life or death, and where the line between science’s promise and its peril becomes frighteningly thin.
