Rudolph "Rudy" Ransom was a Starfleet officer in the 24th century. An exobiologist, he was promoted to captain after making First Contact with the Yridians, a species which Starfleet had previously believed to be extinct. Ransom subsequently took command of the USS Equinox, a Nova-class science vessel, which was pulled into the Delta Quadrant in 2371 by the alien being known only as "the Caretaker."
After the Equinox was stranded in the Delta Quadrant, the crew found themselves in an area of space controlled by the Krowtonan Guard, an aggressive and territorial species. Ransom, refusing to condemn his crew to spending the rest of their lives in the Delta Quadrant, gave the order to traverse the Guard's territory and maintain a course back to Earth. This decision would prove to be a turning point for Ransom, as attacks by the Guard resulted in the deaths of 39 people, over half the crew of the Equinox.
Over the course of the next five years, the Equinox crew discovered that they were ill-equipped to deal with the dangers of the Delta Quadrant. As of 2376, the ship was severely damaged, their dilithium was depleted, and the crew had not eaten in sixteen days. The Equinox had just enough power to enter orbit of an M-class world, where the inhabitants, the Ankari, introduced the crew to nucleogenic lifeforms, beings who originated from an extradimensional realm, whom the Ankari regarded as "spirits of good fortune." Scanning the lifeforms, they discovered that they were emitting high levels of antimatter, and subsequently began to engage in criminal experiments to murder the lifeforms and convert their remains into a source of fuel. Augmenting their warp drive, the Equinox crew were faced with the tantalizing possibility of returning to the Alpha Quadrant in mere months, but also began to come under near-constant attacks by the nucleogenic lifeforms, who were attempting to destroy the Equinox in retaliation for the crew's actions.
The Equinox was saved from destruction by the crew of the USS Voyager, another Starfleet vessel which had been stranded in the Delta Quadrant by the Caretaker. Ransom and his crew initially attempted to conceal their actions from the Voyager crew, but when they were eventually discovered, Ransom was confronted by Captain Janeway. Ransom attempted to justify his actions by quoting Starfleet Regulation three, paragraph twelve, which stated: "in the event of imminent destruction, a Starfleet captain is authorized to preserve the lives of his crew by any justifiable means," but Janeway responded that the protocol did not account for mass murder. Ransom and his crew were subsequently confined to crew quarters, and Janeway ordered her crew to attempt to take the Equinox's engine modifications offline. The Equinox crew was freed, however, by their EMH, allowing them to retake control of their ship. Ransom then had his crew steal Voyager's field generator, which had been modified to protect the crew from attacks by the lifeforms, and set a course for the Alpha Quadrant, leaving Voyager behind.
The Equinox crew soon found that they could not bring their warp drive enhancements back online, as the power relays had been encoded by Seven of Nine, a Voyager crewmember who was being held captive on the Equinox. Ransom attempted to convince Seven to reveal the codes, but decided to force Seven to undergo an extremely invasive procedure whereby her cortical array would be extracted in an effort to find the codes, in response to Seven's refusal to cooperate.
The severity of the actions he had been taking started to weigh heavily on Ransom's conscience, affecting him to the point where he decided to put an end to the experiments and surrender to Captain Janeway. When he gave the order, however, his first officer, Lieutenant Maxwell Burke, mutinied taking command of the Equinox and attempting to destroy Voyager. With the help of Ensign Marla Gilmore, Ransom subsequently accessed the ship's transporter control, and beamed the majority of the surviving Equinox crewmembers to Voyager. Eventually left as the only surviving crewmember on board, Ransom accessed helm control in order to put a safe amount of distance between Voyager and the Equinox, whose warp core was about to breach due to attacks by the aliens. As the core overloaded, Ransom utilized a synaptic stimulator to experience his last moments on the peaceful Tenkaran coast.