Rear Admiral Helena Cain was a Colonial officer from Tauron who served as CO of the Battlestar Pegasus and, with it, Battlestar Group 62. She was one of the few survivors of the Fall of the Twelve Colonies, due to the Pegasus' networks being down at the time of the Cylon attack. Admiral Cain later made contact with a refugee fleet led by Galactica, but was murdered by an escaped Cylon prisoner days later.
Cain was born some 49 years before the Fall, in the early years of the first Cylon War. On the final day of the war, the Cylons stages an offensive in the Helios Alpha system and troops landed on Tauron. Cain's family were trapped inside a wrecked building being used by the Colonial military, and her mother and father killed in the fighting there. She and her sister, Lucy, escaped the building and tried to hide in an industrial area with large containers in, but Lucy was abducted by Centurions when the Armistice signified an end to the war. Her experience of losing her family, and Lucy especially, convinced her that turning back to help others could easily get her killed, and embraced his philosophy with a razor blade.
As an adult, Cain joined the Colonial military, and quickly rose through the ranks. Thanks to political connections, she was promoted "to Rear Admiral over half the Commanders on the list". Following this she was given command of Pegasus.
On the fortieth anniversary of the Cylon armistice, Pegasus docked at the Scorpia Fleet Shipyards ahead of an extensive refit. The ship was hit by a nuclear missile while crew were preparing for shore leave and its defenses down. Cain ran to CIC where she determined the explosion was part of a massive-scale offensive. With Pegasus unprepared for combat, she gave the order to Lieutenant Kendra Shaw to perform a Blind Jump to avoid another two nuclear missiles. Either from the explosion alone or counting crew who had left ship, some 700 were recorded dead. Over the next few days, Cain oversaw repairs and preparations to fight the Cylons, but her determination to get into a fight caused conflict with her XO, Colonel Jurgen Belzen. In an operation to take out a suspected Cylon communications relay, Pegasus fell into a trap set for them and a large Cylon force jumped in. When Colonel Belzen refused to launch the reserve Vipers to fight the increasing Raider, Cain shot him in the head with his own sidearm and made Colonel Fisk her new XO, who complied and launched all squadrons. During the battle, Heavy Raiders boarded Pegasus and began slaughtering the crew. Lieutenant Shaw uncovered proof that there was a humanoid Cylon model, and that computer technician Gina Inviere was one of them. Inviere was captured by the Marines in a scuffle in CIC and, when Pegasus left the battle zone, was subject to advanced interrogation techniques including gang rape on the full consent of Cain, led by Lt. Alistair Thorne.
In the days after the relay fight, Pegasus discovered a refugee fleet of 15 civilian ships. Cain gave orders for the ships to be boarded and stripped of equipment that could be used for maintenance, as well as skilled personnel to be drafted. Among this equipment were parts for the jump drives, which would have made it impossible for ships to escape another Cylon attack. Attempts to take this equipment and personnel succeeded after Lt. Shaw murdered a passenger. Following the incident, Cain took Lt. Shaw under her wing and taught her of her Razor philosophy to harden her.
Six months after the Cylon holocaust, Pegasus was tracking a Cylon fleet when it accidentally encountered Galactica and her civilian ships. Taking over from Commander Adama as military commander of the fleet, Admiral Cain quickly arranges for Galactica 's stores to be replenished from Pegasus 's own, but neglects the civilian fleet, ignoring President Laura Roslin's requests on their behalf.
Cain's chief military objective became identifying a mysterious Cylon vessel sighted in the fleet pursuing Galactica. Cain gives Dr. Gaius Baltar access to Gina to continue the interrogation and learn more about the ship, identified as a Cylon Resurrection ship. The strategic value of knocking out the Cylons' means of avoiding death is not lost on the Colonial military commanders, and so Pegasus and Galactica plan a joint operation to engage the Cylon fleet and destroy the Resurrection ship.
Concurrently with this operation, Admiral Cain and Commander Adama come into conflict over the treatment of two Galactica crew members, Lt. Karl Agathon and Chief Galen Tyrol. Admiral Cain sentences the pair to death for the murder of a Pegasus officer, Cylon interrogator Thorne. Cain and Adama come to the brink of firing on one another's vessels before standing down and agreeing to postpone their disagreements until the Resurrection ship has been destroyed. Nonetheless, each makes plans to have the other assassinated following the successful completion of the operation. Neither plan is carried out, much to the relief of the respective assassins: Captain Kara "Starbuck" Thrace and Colonel Fisk.
Unbeknownst to Cain, Baltar also once had a relationship with a Six, and still has visions of one influencing his decisions. As he interrogated Gina, Baltar fell in love with her. After the Resurrection Ship is destroyed, Baltar tells Gina she deserves justice and helps her escape. Gina kills her guard, steals his gun, and makes her way to Cain's ready room and shoots Cain in the head. After her death, Cain is eulogized by both Colonel Fisk and Captain Thrace, who says they are weaker without her. However, all the weaknesses appear to come from the Pegasus command. Admiral Cain showed a tendency to carry out a vendetta against the Cylons, going so far as to steal supplies and take essential personnel from Colonial ships and leave the survivors defenseless to the Cylons. Col. Jack Fisk was part of a thriving black market until he was assassinated; chief engineer and third in command Barry Garner proved to be incompetent; Colonel Jurgen Belzen was shot dead by Cain, because he refused to carry out one of her orders to attack the Cylons, even after he pointed out to her it could be an obvious trap.