Species

SETI receives a radio transmission containing two components: schematics for faster-than-light propulsion and a DNA sequence with instructions for splicing it with human genes. Government scientist Xavier Fitch uses it to create a hybrid child named Sil in a secure laboratory. Sil grows at an accelerated rate and is unnervingly intelligent, but her violent, instinct-driven behavior alarms the team. When Fitch orders the lab gassed, Sil breaks out.

She escapes on a train, cocooning herself in a sleeper compartment overnight and emerging as a fully adult woman — extraordinary-looking, able to pass as human, and driven by a single biological imperative: find a mate and reproduce. She can shift between her human form and an alien form of H.R. Giger design — massive, tentacled, and designed to kill.

Fitch assembles a pursuit team: mercenary Preston Lennox, biologist Dr. Laura Baker, anthropologist Dr. Stephen Arden, and empath Dan Smithson. They follow a trail of bodies across Los Angeles. Sil is not indiscriminate — she rejects or kills men she instinctively identifies as genetically unfit, selecting for the strongest possible mate with a cold, biological precision that is somehow more disturbing than pure violence.

She eventually connects with Dr. Arden and succeeds in mating. Now pregnant and accelerating, she retreats into the sewer system beneath the city.

The team descends into the tunnels for a final confrontation. Sil transforms fully into her alien body. The fight is brutal. She is destroyed.

In the last shot, a rat moves through the wreckage of her remains in the sewer. It finds one of her eggs and eats it. The DNA is already somewhere else now.