Plot
A plane crashes near a town called Ruby after its cargo escapes. The cargo survives the crash and attacks Ruby's citizens, starting with a lesbian couple, Lisa and Roberta, camping in the woods.
At a swimming hole the next day, John, his girlfriend Kristin, his best friend Tommy, and Tommy's girlfriend Theresa find Lisa's pet Burmese python. Deputy Greg arrives, mentioning that Lisa is missing, and takes the snake. Lisa's body is found, appearing to have been corroded by acids. Greg suspects John, since he works at a plant that uses acids.
Scientist Anton Rudolph meets with NSA Special Agent Parker. The cargo is an abnormally large, 129 ft (39 m) reticulated python genetically engineered in Southeast Asia, blending several species. In the words of Dr. Rudolph, it is, "a perfect killing machine. A 129-foot all-terrain vehicle, capable of speeds exceeding 50 miles an hour, with skin that can deflect an antitank round, enhanced night vision, and a voracious appetite for human flesh". The NSA team plans an assault against the snake.
The snake kills a real estate agent and the agent's client, leaving behind the client and Roberta's bodies. John arrives as the snake leaves, furthering suspicion against him. The sheriff shuts down his brother Brian's plant. When the body of the real estate agent is found with the same acid damage, the sheriff orders John arrested.
The NSA team and Anton arrive, telling the sheriff a story about a psychotic rogue operative committing the murders. He does not believe them, but frees John. Kristin, Tommy, Theresa, and he plan to go on a trip the next morning.
The NSA set up base at a water treatment center. They use radar to find where the snake is likely to be, then have the police set up a perimeter to keep people out of the zone. Believing the snake to be sleeping, the team wastes most of its ammunition on the snake's shed skin. Agent Parker realizes the snake used its skin as a decoy. The snake kills the team, the sole survivor being Anton who keeps himself standing motionless in front of the creature.
Theresa's morning shower is interrupted by the snake. Though she escapes, the snake eats Tommy. Theresa drives away, but the snake follows. It gets in front of her and disables the truck. Theresa hides in a crevice.
When Tommy and Theresa do not arrive, John and Kristin go looking for them, finding the wrecked truck. Theresa tries warning them as the snake approaches, but they cannot hear her. John and Kristin escape using Tommy and Theresa's bikes from the truck. They make it to the water treatment center, where Theresa joins them, and find Anton in shock. The group realizes that they must do something about the snake or it will get to the town. They call Greg on the radio and fill him in on a plan they have devised.
They lure the snake into the water treatment plant by having it chase John through a shaft, while they set a bomb near the entrance. Kristin drops a line down another shaft for John to escape. They pull John out and the python is unable to climb up the shaft. Trapped in the tunnel, the python returns to the doorway entrance. The group returns to the entrance to trigger the bomb, but it does not detonate. Anton runs back in to reset it. Anton detonates the charges while confronted by the snake, sacrificing himself. While the other four are celebrating their success, the python emerges unscathed.
The group flees in Greg's police car, planning to penetrate the snake's hide by luring the snake into a vat of acid at John's plating plant. They are able to push the snake's underbelly into one of the vats, causing the snake to be killed by the acid.
Six months later, Greg has been accepted into Quantico to be an FBI agent, the plant has been reopened as a bar/bike shop where the snake's skin is used as a sales tool, and John finds out that Kristin and he are soon to be parents.
