The story of Stargate SG-1 begins about a year after the events of the feature film, when the United States government learns that an ancient alien device called the Stargate can access a network of such devices on a multitude of planets. SG-1 is an elite Air Force special operations team, one of more than two dozen teams from Earth who explore the galaxy and defend against alien threats such as the Goa'uld, Replicators, and the Ori.

The exploits of FBI Special Agents Fox Mulder and Dana Scully who investigate X-Files: marginalized, unsolved cases involving paranormal phenomena. Mulder believes in the existence of aliens and the paranormal while Scully, a skeptic, is assigned to make scientific analyses of Mulder's discoveries that debunk Mulder's work and thus return him to mainstream cases.

Years ago, the Taelons came to Earth, offering friendship and technology to humanity. But there are those who believe the Taelons have more sinister motives.

Sydney Fox is a professor and globe-trotting "relic hunter" who looks for ancient artifacts to return to museums and/or the descendants of the original owner. She is aided by her linguistic assistant Nigel and occasionally by her somewhat air-headed secretary Claudia. She often ends up battling rival hunters seeking out artifacts for the money.

Richard Greico leads a team of electrical workers who stumble across a terrifying parallel universe. While investigating a strange power source in an abandoned building, the workers find themselves sucked into an underworld teeming with massive, man-eating, spider-like monsters. The bloodthirsty arachnid-human hybrids stalk and kill their victims one by one, leaving the dwindling group of survivors to fight back with just their wits and a handful of primitive weapons.

A team of scientists explore a new planet and find much more than expected.