"Eye of the Beholder" is the 170th episode of the science fiction television series Star Trek: The Next Generation, the 18th episode of the seventh season. This episode holds the distinction of being the first instance in any Star Trek TV series or film where the inside of a starship's warp nacelle is depicted, and the only instance until 2002's Star Trek: Enterprise episode "The Catwalk".

Lieutenant Daniel Kwan kills himself by jumping into the plasma discharge in one of the warp nacelle tubes aboard the Enterprise, the only oddity being his comments about "they were laughing at me" and "I know what I have to do," before jumping. Captain Picard assigns Worf and Deanna Troi to investigate the death. Kwan's personnel logs and quarters reveal no traces of depression; in fact, he appeared to be happy to spend the next few days with his girlfriend, Ensign Calloway, and only had a slight but normal dislike for his superior Lieutenant Nara.

They talk to Nara at the nacelle but find that she had nothing against Kwan. Troi stands at the platform overlooking the plasma discharge and is suddenly awash with emotions, disorienting her. Dr. Crusher determines that her empathic senses were overloaded and suggests rest. Troi and Worf discuss that she may have been affected by an empathic "echo" left by Kwan, who also had weak empathic abilities. They return to the nacelle, where Troi experiences a series of visions: that of a woman backing away in fright from a red-haired man; equipment from Utopia Planitia, the starbase where the Enterprise was constructed; and later the same woman kissing another man in a closet. Worf breaks her out of these visions, and they determine that they were from events eight years ago during the Enterprise' construction. Troi is able to recognize the red-haired man as Lieutenant Walter Pierce, who is currently serving aboard the ship; Pierce had been Kwan's superior at Utopia Planitia as well. They speak to Pierce, but he claims to have no knowledge. After they leave him, Troi admits to Worf that she could not read Pierce, and believes him to also be partially empathic. As they prepare to retire for the night, Troi and Worf fall into a deep kiss, and spend the night together.

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