"Sarek" is the 23rd episode of the third season of the American science fiction television series Star Trek: The Next Generation, and the 71st episode overall. It was originally released on May 14, 1990, in broadcast syndication. The story for the episode was created by Marc Cushman and Jake Jacobs, with the teleplay written by Peter S. Beagle. "Sarek" was directed by Les Landau. Set in the 24th century, the series follows the adventures of the crew of the Federation starship Enterprise. In this episode, Sarek (Mark Lenard), the father of Spock and a highly regarded but elderly ambassador, is ferried by the Enterprise on his final mission for the Federation. While he is aboard the ship, the crew experiences an outbreak of irrational anger amongst themselves. It is revealed that Sarek has Bendaii syndrome, which is telepathically causing the problems among the crew. It is only resolved after the Vulcan mind melds with Captain Jean-Luc Picard (Patrick Stewart).

The appearance of Lenard was originally suggested by Gene Roddenberry as an alternative to an appearance by Leonard Nimoy, as it was suspected that it would be too expensive to have the latter actor reprise the role of Spock on television. Roddenberry had previously barred references to Star Trek: The Original Series in The Next Generation; the inclusion of Sarek in his namesake episode, along with a mention of Spock, was seen by the crew of The Next Generation as a breakthrough, allowing them to reference The Original Series more freely in the future. Sarek's failing health was intended to be a reference to the declining health of Roddenberry. "Sarek" received Nielsen ratings of 10.6 percent; it was praised by critics, who lauded the performances of both Lenard and Stewart.

...
Wikipedia