Corruption (1968)
Corruption is a 1968 British film directed by Robert Hartford-Davis, from a screenplay by Derek Ford and Donald Ford, and featuring Peter Cushing, Sue Lloyd, Noel Trevarthen, Kate O'Mara, David Lodge, Wendy Varnals, Billy Murray, and Vanessa Howard. Corruption stars horror icon Peter Cushing in a shocking and atypically villainous role as a homicidal doctor.
More at Wikipedia.