Rachel Garrett was a Starfleet officer and captain of the USS Enterprise-C in 2344.
In that year, the Enterprise-C, under Garrett's command, responded to a distress call from the Klingon outpost at Narendra III, which was under attack by four Romulan Warbirds. As the Enterprise-C was defending the outpost, the weapons discharges resulted in the creation of a temporal rift, through which the badly damaged Enterprise-C drifted, arriving in the year 2366.
Upon emerging from the rift, the crew encountered their ship's immediate successor, the USS Enterprise-D, whose captain, Jean-Luc Picard , informed them that the Federation was at war with the Klingon Empire, and were on the brink of defeat. Initially, Garrett was prepared to remain in that timeframe and assist the Federation's war efforts, but it was eventually discovered that the Enterprise-C's journey through time had resulted in the creation of an alternate timeline, and that, if they wished to restore the proper flow of history, the Enterprise-C would have to return through the rift, in the middle of the battle with the Romulans. Garrett initially balked at this idea, noting that they were hopelessly outmatched by the Romulans, but Picard pointed out that, if a Federation starship were to sacrifice itself in defense of a Klingon outpost, such an act would be seen as extremely honorable by the Empire, and would perhaps avert decades of war. Garrett eventually conceded, and prepared to take her ship back through the rift.
However, before the Enterprise-C could depart, both ships came under attack by a Klingon Bird-of-Prey, resulting in Garrett's death. The timeline was eventually restored when Lieutenant Richard Castillo took command of the Enterprise-C, and returned the ship through the rift.