Daniel O'Kane (also known as Patient Zero or simply Zero) was a sensitive. He was raised by his mother and father at Hawthorne with his sisters and his brother, Jeremiah. On 13 August, 1945, Daniel was taken over by an evil force from another plane of reality, a "reservoir of evil" (HOMEVID: The Zero Imperative) which was in actual fact the Yssgaroth. (PROSE: Preternatural Nights) Under its influence, he killed his parents and sisters.
As he was too young to be hanged, Daniel was sent to an asylum and moved from one to another for forty years. He had a son named Peter Russell who was adopted by Jeremiah. Jeremiah wanted Daniel at Hawthorne where he could keep and eye on him whilst Dr Colin Dove wanted to use him at perihelion to unleash the reservoir. Daniel was transferred in 1994 and was kept in Room 0 where he was known as Patient Zero and frequently sedated.
Daniel astral-projected and killed ten people, including William Bruffin and Dr Dove. He wanted to rest and, when the reservoir took over Peter at perihelion, Daniel jumped in front of his knife and saved Liz Shaw. He died and the catastrophe was averted. (HOMEVID: The Zero Imperative) Giles later evoked the Patient Zero affair among past cases handled by P.R.O.B.E., in the first video case file he recorded as the new Director of the Bureau. He included archival footage of Patien Zero himself. (HOMEVID: First Entry)