"Ashes to Ashes" is the 138th episode of Star Trek: Voyager, the 18th episode of the sixth season. It has an average fan rating of 4/5 on the official Star Trek website as of September, 2009.

An alien contacts Voyager, claiming to be a deceased member of the crew, Ensign Lyndsay Ballard. She explains that an alien race, the Kobali, reanimated her after her coffin was buried in space. The Kobali reproduce by altering the DNA of dead individuals of other races, though such people are (at least initially) prisoners of the Kobali so that they may more easily adjust to their new lives. Ballard escaped from her 'new' family, stole a ship, and spent 6 months searching for Voyager.

When she finds Voyager, she is under attack from a Kobali vessel. Disabling the pursuing vessel, she makes audio contact with Voyager—only to be disconnected when Mezoti, an adolescent former Borg drone, accidentally closes the channel in an attempt to notify Captain Janeway.

When contact is re-established, Ballard is brought to Sickbay, where she retells the story of her death. Harry Kim, who was involved with Ballard, is present to confirm the details, and the Doctor confirms that the alien's DNA contains portions that match Ballard's medical records.

When the Captain clears Ballard for duty, she attempts to return to her "old" life, but finds adjustment difficult—the Doctor has managed to restore her physical appearance, but biologically, she's still Kobali (as there wasn't enough human DNA in the ensign's body to revert her). She discovers that fact for herself all-too-clearly when she attempts to eat her favorite food in the Mess Hall, and finds that it suddenly tastes 'metallic' and unappealing.

Eventually, Q'Ret - Ballard's Kobali "father" - returns, demanding the return of his "daughter," Jhet'laya. After a tense meeting in the briefing room (which Ballard ends prematurely), she finds herself in the Mess Hall, depressed and isolated. When Harry Kim attempts to console her, and suggests that they alter one of Tuvok's meditation holoprograms as a prank, Ballard suffers a painful "reversion" of her Kobali physiology.

In Sickbay, the Doctor discovers that a pathogen that was introduced into Ballard's bloodstream is forcing Ballard's body to reject the Doctor's improvised "reconstructive surgery." Ballard must visit Sickbay twice daily if the treatments are to remain effective. Ballard loses her temper upon hearing that she would, essentially, be confined to Sickbay for the rest of the 75-year journey, and lashes out vocally and physically, shouting angrily in untranslated Kobali.

Appalled at her new, more "volatile" Kobali personality, Ballard discovers that Voyager is no longer the home she once knew; corridors that she once walked with familiarity are now alien, she is unable to remember her human family due to the Kobali's alterations, and her new Kobali personality is too emotionally volatile.

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Wikipedia