Sean Delaney was a major character in the Series 15 episode Fear. He was a psychiatrist and an old friend of Leo Dalton.
Sean asks Leo to look into the mysterious death of one of his patients, a troubled teenage girl named Eve. Her death was put down to sudden death syndrome, but Sean believes there was another cause. Sean reveals that eve believed she was possessed by demons - Sean thought she was being abused by her father, but later came to doubt this. He arranged an exorcism in his home for Eve, believing it might help her get through her fears, but it went wrong. Eve died in her bed soon after. He also reveals to Leo that he is terminally ill and doesn't see the point in getting therapy. When Eve's younger brother John begins exhibiting similar fears, Sean pretends to 'exorcise' the demons he is afraid of and allows them to 'possess' him, freeing John. Unfortunately, in spite of Leo's efforts, Sean then commits suicide by jumping from a tall building.