The Green Trail(1975)

The Green Trail is a mystery series set in the USA that follows Thomas Norton, a lie detection researcher who works with courts and private industry. When Norton casually attaches electrodes to a plant in his office, he discovers it responds to emotional stimuli in unexpected ways. Intrigued, he deepens his investigation, keeping the plant wired in his lab. The case takes a dark turn when a woman living in his building is murdered in the lab—and the plant becomes the only witness to the crime. Norton must decode the plant's mysterious signals to uncover the truth behind her death.