In 1984, a Russian research team goes below the surface to find out what secret the world's deepest borehole is hiding. On their expedition, something unexpectedly gruesome awaits the researchers.

When Environmental Protection Agency inspector Steve Malone travels to a remote military base in order to check for toxic materials, he brings his family along for the ride. After arriving at the base, his teenage daughter Marti befriends Jean Platt, daughter of the base's commander, General Platt. When people at the base begin acting strangely, Marti becomes convinced that they are slowly being replaced by plant-like aliens.

Underwater deep-sea miners encounter a Soviet wreck and bring back a dangerous cargo to their base on the ocean floor with horrifying results. The crew of the mining base must fight to survive against a genetic mutation that hunts them down one by one.