The Returners are thirty-three Colonial citizens, most known to be long dead, who reappear, apparently very much alive, in an old Colonial ship, Medivac 12, encountered by battlestar Galactica as it passed by an old Colonial battlefield of Colonial ships in a region of space very far away from the Twelve Colonies (Battlestar Galactica 0).
Laura Roslin, reading from the Sacred Scrolls, notes a passage that "The dead shall return in an ark of fire." Medivac 12 is suffering from hull breaches and internal fires as its inhabitants ward off Cylon Centurion attacks.
While Commander William Adama and his son, Lee Adama, strongly believe the people to be Cylon constructs similar to Humanoid Cylons, Caprica-Valerii tells them that these people are not Cylons (Battlestar Galactica 1).
Kara Thrace is unsure of the nature of these people, particularly after she encounters her dead fiancé, Zak Adama, aboard the ship (Battlestar Galactica 0). Anastasia Dualla's brother, Darrin, also appears on the derelict ship.
Some of the Returners escape via zip pods to other ships in the Fleet, despite Galactica's quarantine order (Battlestar Galactica 1). The people, unwillingly or intentionally, spread a contagion that incapacitates most of the crew (Battlestar Galactica 2).
Gaius Baltar, investigating the craft, discovers that the Returners are Cylon constructs of a sort. The beings are clones implanted with memories of the dead, used by the Cylons to study human nature in preparation for the creation of the twelve humanoid Cylon models. Billy Keikeya, pouring through available records, confirms that every one of the Returners were people who died while in some kind of flight, and were not on the ground or in a building at the time of their death (Battlestar Galactica 3).
List of Returners
The following is a list of known Returners, including how their originals had died and how long ago they died, in relation to the events of the comics.
The concept of the deceased returning occurs in the main continuity as the fleet encounters a miraculously alive Kara Thrace (TRS: "He That Believeth In Me"). Considering the issue, Lee Adama muses about what would happen if Zak returned in a similar fashion, and Starbuck herself considers the possibility that she is a Cylon construct similar to that described above.