Doctor Who: The Taint (Eighth Doctor Adventures, #19)

The Tardis lands in 1963, and soon the Doctor and Sam become involved in the psychological experiments being performed by Charles Roley on former sufferers of mental illness - he is probing the psyches of six people who believed they've been possessed by the devil. While the Doctor is horrified to learn the full extent of the side-effects brought into being by Roley's research, Sam heads off to experience the swinging London of her parents' youth. Instead she finds deadly danger at the hands of a sinister half-man half-robot double act whose agenda is inextricably linked to Roley's test subjects.