As a young man, John had fair hair which was cut short. He typically wore a cap and was dressed in the warm winter gear typical of the residents of the Farrell Shelter. As an older man, John's face was covered with many wrinkles and he let his hair grow to shoulder length. He dressed in the warm Eskimo clothing favored by the residents of the Bradley Shelter. For his funeral he was wrapped in bandages like a mummy, leaving his face exposed.
John had a kindly nature, which was seen when he rescued Vilma Fachiri and played his guitar for her while she was recuperating. Even after learning that she was a Type-V mutant, he seemed to empathize with her situation, and even offered to let her suck his blood as a means of attempting to convince her to stay. When she later returned, he took her aside and begged her to forgive the actions of his father Keiran.
Despite the massacre of the inhabitants of the Farrell Shelter and Victor Byron's severing of his arm in the middle of a blizzard, both of which he survived, John never forgot Vilma's attitude or her kindness. He passed this on to his grandson Arthur, which was enough to convince Arthur to trust that she would receive him favorably.
John formed a close relationship with Vilma, growing to see her as a mother figure during her time in the shelter. He maintained his belief in her through the years, and requested that Arthur bring her to see him before he died. Their reconciliation and Vilma's assurance that she would help his grandchildren allowed John to die in peace. He had a close relationship with his grandson, instilling in him the need to see the Merlin project through, and accepted Haruka, Athur's fiancée, as one of his family.
Born in ES 56 a year after the Geo Catastrophe plunged the Earth into a prolonged impact winter, John lost his mother at some point and was raised by his father Keiran. He found Vilma unconscious in the middle of a blizzard in ES 69 after she had fallen off a cliff during a fight with some mutant humans and was able to take her back to the Farrell Shelter. Here Vilma regained consciousness to the sound of John playing a guitar, the first time she had heard such a sound in years, which deeply moved her. John's father Keiran nursed her back to health, discovering that she was a Type-V mutant, but theorized that her condition was caused by a virus, telling her that she was human like he was. After Vilma was able to walk around a bit, John overheard her telling his father that she did not wish the Cognate to suffer again in the shadow of humanity. Once she was fully healed, the shelter's residents met to decide what to do, and were convinced by Keiran to cooperate with the Type-V mutants. Vilma was allowed to return to Victor Byron as a peace emissary. Just before she left, John begged her not to go, telling her that he liked her and asking her to stay, even offering to let her suck his blood when she got hungry.
After Vilma returned to Victor and convinced him to make peace with the humans, it was agreed to dine with the residents of the Farrell Shelter following the exchange of several letters. After the Type-V mutants arrived, John pulled Vilma away and begged her to forgive his father. The rest of the group was led into a specially prepared room, which turned out to be a trap set to kill them, with Zapolska succumbing to some poisoned food. Vilma confronted Keiran, who revealed that his plan was to kill the others, but spare Vilma, who he asked to act as a mother to John. Victor in turn revealed that he had suspected a trap, but allowed the Cognate to be led into it to show Vilma how treacherous humans could be. He then placed her in the difficult position of having to choose between them or the humans. Enraged at the betrayal of her trust, Vilma had Victor promise to spare the Farrells before opening the room's doors. Victor kept his promise, but unleashed Jacco and Morse on the rest of the shelter's inhabitants, who they massacred. He then took Keiran and John outside the shelter. After telling John that he deserved to die for his innocence, which had bewitched Vilma, he cut off his right arm. Vilma quickly bound the stump of John's arm, but coming into contact with his blood stirred her bloodlust, forcing her to bite her own forearm to stop herself from attacking John. When Victor tried to stop her, she fell on him in turn, while Keiran picked up his son and walked away in the middle of a blizzard.
John survived his wound and went on to have a family of his own. He eventually lived in the Bradley Shelter, where he served as a doctor and teacher, leading him to be addressed as "Dr. Farrell" and earning the respect of many of the residents. John was the last surviving relative of his grandson Arthur, who learned the story of the Farrell Shelter as well as of his grandfather's faith in Vilma. This led to him believing that Vilma would be trustworthy after the Type-V mutants arrived in the remains of St. Louis in ES 126.
Shortly after their arrival, Morse was killed by Arthur while he was out hunting. Arthur took his body back to the group and challenged them, bluffing his way out of being targeted by appearing to have strapped himself with sticks of dynamite. He asked for Vilma, telling her that his grandfather wished to see her and that he would bring her back safely. Vilma was taken to a dying John, who asked her to forgive him, but was told that she was the one to apologize. After asking her to help his grandchildren, his last words were to tell Arthur to restart Merlin as the last hope of civilization. That night John's funeral was held in the hall of the Bradley Shelter, which was attended by Vilma after Arthur convinced her not to return to Victor following her defeat of Jacco, who had attempted to kill her.