Extinction (Star Trek: Enterprise) - Plot

Plot

A group in biohazard suits chases a humanoid through a jungle, then uses blow torch-like weapons to incinerate it.

On Enterprise, Commander Tucker brings Sub-commander T'Pol some Georgia peaches to thank her for helping him sleep. After coaxing her into tasting one, T'Pol is called to the command center by Captain Archer.

Archer tells her that he found a nearby planet that the Xindi recently visited from the information database acquired from the Osaarian marauders in "Anomaly." He decides to visit it to learn more about the species.

The two beam down with the ship's security chief, Lt. Reed and Ensign Hoshi Sato. They discover a Xindi shuttle along with two dead crewmembers, one of whom has been incinerated. Archer, Sato and Reed begin experiencing changes to their physiology. They are transformed into a species with a different language. They attack T'Pol, rendering her unconscious.

When she comes to, she works to convince them that she wants to help them and they should set her free. Archer, who seems most sympathetic to her, is able to convince the others despite the protests of Sato, who seems a bit jealous of his interest in her and a bit suspicious that she is not one of them. After T'Pol gets the universal translator working, she learns that her companions have been inculcated with an overwhelming desire to reach a place called Urquat, the homeland of their species.

The Enterprise crew determines that the human members of the away team have been transformed biochemically. Commander Tucker takes a shuttlepod to the surface with an away team of MACOs equipped with biohazard suits. Reed is captured and returned to the ship. T'Pol opts to stay with Archer and Sato.

Dr. Phlox determines that Reed was infected by a mutagenic virus which transformed his DNA. He concludes that T'Pol's Vulcan genetics rendered her immune, but he will need a sample of her DNA to synthesize a cure. Two "containment ships" from an alien race arrive, demanding that they be allowed to board Enterprise and eliminate Reed because the virus wiped out millions of their people. Tucker refuses to allow this, but invites their leader, Tret, aboard. Tret tells Phlox and Tucker that the original inhabitants of the planet, the Loque'eque, created the virus after they were rendered sterile, in an effort to transform alien visitors into their species and avoid extinction. Tret does not believe it is possible to cure the virus and sends a team to the planet's surface to incinerate Archer and Sato.

Archer leads Sato and T'Pol to Urquat, but they find it to be the ruins of an ancient civilization. When the containment team from Tret's ship arrives, the three fight them off. In the process, one of the men's bio-suits is punctured, and the rest of his team incinerates him. The team traps the three Enterprise crewmembers, but before they are incinerated Trip transports down with a team of MACOs and takes out the containment team. The group returns to Enterprise.

The containment ships pursue Enterprise, forcing it out of warp. Tucker asks Tret to allow Phlox more time to synthesize an antidote, but Tret refuses and prepares to board the ship. Before he can, Phlox presents Archer and Sato to him—mostly restored. Enterprise provides Tret with the antidote.

Phlox continues treating Archer, Reed and Sato as they continue undergoing physiological changes while returning to normal. Phlox plans to destroy the last sample of the virus, but the captain orders him not to, saying it was the last effort of an extinct species to preserve itself and should be preserved as a testament to their civilization.