Star Trek: The Next Generation Episode 48: Shades Of Gray

VHS, PARAMOUNT

While Riker (Jonathan Frakes) is conducting a geological survey on Strata Four, his thigh is pierced by a small thorn which kills all feeling in that leg. Aboard the Enterprise, Dr. Pulaski (Diana Muldaur) determines that the thorn contains a mysterious organism that is coursing through Riker's nervous system. Pulaski tells Picard (Patrick Stewart) that she cannot kill the organism without also taking Riker's life. In order to keep Riker's brain functioning, Pulaski begins to electronically stimulate his memory and notices that positive memories seem to feed the growth of the organism. Pulaski surmises that negative emotions might destroy the organism... but could they also destroy Riker?.