Jeremiah O'Kane was the former director of the Hawthorne clinic, who continued to live in the clinic's grounds in his retirement. The clinic had in fact been run by his family for some time, but Jeremiah's father, mother and two sisters had been murdered by Jeremiah's brother Daniel forty years earlier - the clinic was built in a place prone to evil, murderous possession of victims at certain times in history. The brother had been sent to an asylum following the murders, while Jeremiah took over the running of the clinic. He also raised his deranged brother's son, Peter Russell, telling him only that he was adopted. Russell declined to enter the medical profession - a decision which drove a wedge between the two - but instead became a very wealthy businessman.
In his later years, O'Kane handed over the directorship to Dr. Colin Dove and, despite his fading memory, continued to act as a mentor to the doctors working there, including William Bruffin. However, O'Kane and Dove knew another cycle of evil was imminent and set up a bizarre experiment. They organised the return of O'Kane's brother as an inmate of the clinic, and when government cut-backs forced the closure of hospitals, Russell stepped in to finance the clinic and keep it open. Apparently part of their plan, or certainly Dove's plan, was to bring the father and son together at the appointed time and create 'perihelion' - somehow allowing chaos to erupt into the world. Dove discussed this with O'Kane, but his involvement was questionable. O'Kane also tried to mend fences with his returning adopted son, but it was only after Russell was possessed by the same evil spirit and his self-sacrificing father saved Liz Shaw from him, that the 'perihelion' was avoided and life returned to normal at the clinic. O'Kane and Russell tried to rebuild their relationship. Dr O'Kane bore a striking similarity to Liz Shaw's former UNIT colleague 'The Doctor', though this does not seem to have been any great surprise to her.