The Green Trail (1975)
Set in the USA, the plot concerns Thomas Norton, a researcher in the field of lie detection, who provides his services to courts and private industry. One day he idly attaches electrodes to a plant in his office, and is surprised to find it responds with recognisable emotional reactions to the stimuli he gives it. He pursues this research, and keeps a plant wired up in his lab. When a woman who lives in his building is mysteriously murdered in his lab, the plant is the only witness to the crime.
John Ginsberg
Thomas Norton
Mark Bennett
Nick
Margaret Stakowski
The Lieutenant
Burton
Betty Segal