The Ghost & Mrs. Muir (1968)

S1E4 The Ghost Hunter

Claymore introduces a visitor interested in photographing the house, claiming to be an architecture student. However, once the Muirs depart for the night, Captain Gregg mistakes him for a thief and attempts to frighten him off. Unbeknownst to Captain Gregg, the stranger is actually a parapsychologist on a mission to uncover the ghost of Gull Cottage and reveal its presence to the public.