The Taurean system was an uninhabited planetary system consisting of a small star and at least two planets. It was located at the extreme edge of a sector visited by both Earth and Federation starships since the early 22nd century but still considered unfamiliar by Starfleet in the mid-23rd century.
At least 150 years prior to 2269, Planet Two had been colonized by a humanoid species. In 2119, the first Earth ship was reported as missing. In 2269, the Federation had a recent discussion with the Klingons and the Romulans, in which it was revealed that ships were disappearing every 27.346 star years. The USS Enterprise was ordered to investigate the cause of the disappearances. On approach to the system, a signal sent from the Taurean system, by the female who lived there, temporarily affected the starship's male officers and thereby lured the vessel to the second planet, which was evacuated shortly thereafter. (TAS: "The Lorelei Signal")