The Lead Inmate was a patient at the Vannacutt Psychiatric Institute for the Criminally Insane. Eventually, in 1931, he grew tired of the torment he and the other patients were suffering under Dr. Vannacutt, and led a revolt among the patients against the staff. After Vannacutt activated the asylum's lockdown to stop the patients from escaping, the Lead Inmate and several other patients tortured Vannacutt to death, then apparently perished when a fire started in the sealed asylum.
After the Lead Inmate died in the asylum, the Baphomet Idol kept his ghost bound to the building, along with the ghosts of everyone else who died in the revolt.
In 2007, while Ariel Wolfe and Desmond Niles are searching the asylum for the Baphomet Idol, the Lead Inmate locks Ariel in a padded cell and appears to her, showing her a vision of his role in the 1931 revolt. When Ariel wakes up from the vision, she is in a straightjacket and the Lead Inmate is gone.
Later, when Ariel has another vision in the asylum washroom, the Lead Inmate appears to her in the vision, telling her that she needs to destroy the Baphomet Idol and free him and the other trapped souls. He then shows her that the Idol is in a chamber hidden behind one of the furnaces in the asylum's crematorium.
After Ariel removes the Idol from the facility by sending it into the asylum sewer and out to sea, the Lead Inmate and the other ghosts are freed from Baphomet's will and turn on Vannacutt. The Lead Inmate and several of the other ghosts appear to Ariel and Vannacutt in the washroom, and Ariel steps aside and allows the ghosts to take their revenge on Vannacutt. The Lead Inmate and the other ghosts then tear the powerless Vannacutt apart for what he did to them in life, then cross over.