Ransom was a Starfleet exobiologist who achieved the rank of captain after making First Contact with a race called the Yridians. 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."
Early into the Equinox's voyage home to Earth, she suffered the loss of half her crew when Ransom gave the order to traverse through alien territory of the Krowtonan Guard. Over the years, Ransom and his crew continued to endure great hardships, losing more crew and resources. Around mid-2376, however, the Equinox made contact with one of the Delta Quadrant's more benevolent races, the Ankari. During this contact, the Ankari decided to bless Ransom's crew by showing them beings from another dimension, what the Ankari believed to be spirits of good fortune. Tricorder scans taken by the crew revealed that these entities were nucleogenic organisms and that their biology could be broken down into an isolytic compound that could be used as starship fuel. Without revealing his intentions, Ransom made a trade with the Ankari, exchanging an energy converter in return for one of the devices used to summon the nucleogenic aliens. When the Equinox was underway again, the crew began summoning and killing the creatures in order to power their modified warp drive. The alien compound proved to be a very efficient fuel source and reduced the ship's journey to Earth by an impressive margin, but Ransom's slaughter of the aliens incurred their wrath and they began attacking the Equinox in waves, determined to destroy the ship.
Several weeks after the attacks began, the Equinox was discovered by the USS Voyager. 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 Ransom had been taking started to weigh heavily on his 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 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.