The first episode starts at the scene of Viking 1 unmanned probe landing on the surface of the planet Mars in July 1976. A narrator explains that the purpose of the probe is to determine whether Mars is inhabited. As the narrator is speaking, the viewer becomes aware that there are two viewpoints at NASA amongst the scientists who launched the probe: One group obviously believes Mars is uninhabited, the other is open to the possibility of indigenous life on the planet. Each has its convincing arguments, but ultimately the probe indicates that Mars does not harbour life. At the close of the scene the camera pans back to show a larger view of the probe's landing area, with what appears to be indigenous Martian settlements in the surrounding terrain, with the narrator noting that, "If the probe had landed just a few miles further on, things might have been different." Afterwards the opening credits roll.