Space: 1999 S01 E22 The Troubled Spirit

"The Future Is Fantastic!"

Dan Mateo, hoping to unlock the secret of communication with plants, unleashes a killing force from the depths of his own mind. This macabre spectre seeks vengeance for Mateo's horrible death—which has not yet occurred. Bridging the span between science and the supernatural, the Alphans hope to break the cycle and exorcise the ghost without killing the man.