"Metamorphosis" is a second season episode of the original science fiction television series, Star Trek, first broadcast on November 10, 1967, and repeated July 19, 1968. It is episode #38, production #31, written by Gene L. Coon and directed by Ralph Senensky.

In this episode, a shuttle crew from the USS Enterprise encounters a man out of history and his mysterious alien companion.

Federation Commissioner Nancy Hedford is being ferried to the Enterprise aboard the shuttlecraft Galileo. Though supposedly a seasoned diplomat, Hedford behaves in a temperamental manner. Kirk is annoyed, but McCoy explains that she has a potentially fatal condition, Sakuro's Disease, and needs immediate treatment aboard the Enterprise. The ship will then transport her to Epsilon Canaris III, where she will conduct vital peace talks between the planet's warring factions. Suddenly, a strange glowing energy field appears in the shuttlecraft's path, disables its systems, and pulls it down to a nearby planetoid, which has an Earth-type atmosphere. Kirk tries to contact the Enterprise for assistance, but all signals are blocked by some unknown phenomenon and the shuttlecraft has been rendered totally inoperable.

Soon after landing, a fit, handsome young man calling himself Cochrane appears. He tells the party that he has been marooned on the planet for years, that there is a damping field in effect, and that they are stranded just as he is. Cochrane takes them to the shelter he has built from material salvaged from his crashed ship, and he explains his survival and his relationship with an alien being. When he reveals his full name, Kirk, Spock and McCoy are stunned to discover that he is none other than Zefram Cochrane, the inventor of the Federation's "warp drive" technology. Cochrane explains that as an old man, he took one last flight - intending to die in space - but his crippled ship was intercepted and rescued by a strange alien entity, which has restored him to youth and can keep him alive indefinitely. He explains that he has been living with the entity for 150 years, and the Enterprise crew observe that he has a symbiotic relationship with the energy force, which he calls "The Companion". When Cochrane begins to talk about this relationship, and the pleasure it gives him, Hedford becomes critically ill. After "the Companion" attacks Spock during an attempt to repair the shuttle, Spock deduces that the entity is largely composed of electrical energy. Kirk, Spock and Cochrane attempt to disable "the Companion" with an improvised electrical disruptor, but the attack fails. "The Companion" retaliates violently, and only Cochrane's intervention saves Kirk and Spock from being killed.

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