The Immunity Syndrome (Star Trek: The Original Series)  "The Immunity Syndrome" is the eighteenth episode of the of the American science fiction television series "". Written by Robert Sabaroff and directed by Joseph Pevney, it was first broadcast on January 19, 1968. In the episode, the crew of the "Enterprise" encounters an energy-draining, space-dwelling organism. The Federation starship "USS Enterprise" receives a garbled message from Starfleet mentioning the USS "Intrepid", a Federation starship crewed entirely by Vulcans. First Officer Spock suddenly looks shocked and announces that he has felt the "Intrepid" "die". Starfleet then succeeds in making contact, and orders Captain Kirk to investigate the Gamma 7A system, the last known position of the "Intrepid". Ensign Chekov reports that the sensors show no life readings in the system of a billion inhabitants. Meanwhile, Spock is examined by Chief Medical Officer Dr. McCoy in sickbay, where he explains he felt the combined shock and terror in the minds of 400 of his fellow Vulcans aboard the "Intrepid" as they died. McCoy is amazed that Spock felt anything over the distance involved, but admits there is a lot about Vulcans he still doesn't understand. Spock returns to the bridge just as Lt. Uhura announces she has lost contact with Starfleet. Kirk has Spock scan a dark zone that appears on the main view screen. Suddenly, half the crew are sickened or faint. Spock is unable to determine the nature of the zone, but suggests it is some kind of energy turbulence, and possibly responsible for the death of the system inhabitants and the "Intrepid" crew. Kirk has Chekov launch a sensor probe into the void. The probe transmits a piercing, high-pitched noise before contact with it is lost. Kirk orders the ship into the zone, and as it enters, the piercing sound returns and all the stars disappear from the main view screen. McCoy then reports that the crew are getting worse, and Chief Engineer Scott reports a loss of power. Spock surmises that the ship has entered a sort of negative energy field that interferes with biological and mechanical processes. The "Enterprise" appears to be accelerating of its own accord, and the ship's engines seem to be operating in reverse: forward thrust slows the ship down. Kirk suggests that all available power be channeled into a massive forward thrust, in the hope of breaking free of the zone, but the effort succeeds only in bringing the ship to a halt.