The episode's story mainly consists of a relationship between Chief Medical Officer Julian Bashir and Melora Pazlar, an Elaysian whose species' physiology is generally incompatible with the strength of artificial gravity found on most humanoid communities, including Deep Space Nine. As a result, Melora must use external mechanical apparatus to exist comfortably on the station. When she is in her quarters she can, and frequently does, adjust environmental settings to simulate her accustomed habitat. However, because of her physical condition, Melora is argumentative, even rude, in insisting that she not be shown any undue accommodation. Nevertheless, Julian sees through Melora's barriers and the two become romantically involved.
Meanwhile, just as Quark is about to conclude a very lucrative deal over some historical relics with a man named Ashrock, an old acquaintance of his named, Fallit Kot walks into his bar. The two have history, with Kot declaring to Quark that he is on DS9 to settle certain "debts". Chief of Station Security Odo suspects Quark sold-out Kot when the two were caught in a Romulan larceny caper eight years ago, and now Kot is back to kill his former partner in crime. However, when questioned by Odo, Kot denies any ill intentions toward Quark.
Later in the episode, Bashir develops an application of a neuromuscular adaptation theory that could allow Melora to comfortably walk without the help of any of the equipment she currently uses. Even after successfully participating in tests of Bashir's new engineering technique, Melora has misgivings. If she goes through with the procedure, she will no longer be able to live in the low-gravity environment of her home world. Lt. Jadzia Dax, during a survey mission with Melora to the Gamma Quadrant, compares her predicament to that of "The Little Mermaid".
Back on DS9, Kot attacks Quark in his quarters, but Quark plays to Kot's greed by offering him 199 bars of gold-pressed latinum (the proceeds of his deal with Ashrock) in exchange for his life. Kot takes the deal, and they go to meet Ashrock at an airlock. Quark's deal is closed, but Kot shoots Ashrock and takes the relics in addition to the latinum. Kot forces Quark to go with him, and they come across Melora and Dax, who are returning from their survey. Kot takes all three hostage aboard the runaboutOrinoco.
Commander Sisko orders the runabout to be held in a tractor-beam. Kot demands they be released, shooting Melora to prove his point. Sisko lets them go, but takes Bashir and Chief O'Brien with him in the runabout Rio Grande. The Orinoco is pursued through the Wormhole. Kot orders Dax to fire on the Rio Grande but as she refuses, she notices that Melora is not only still alive, but crawling toward a console controlling the ship's gravity. In her element after shutting down the gravity, Melora overpowers Kot, who is taken into custody. Sisko orders the runabouts to head for home.
After finally deciding against going through with Julian's neuromuscular procedure, Melora and Julian enjoy the chef's serenade at the Klingon restaurant where they had their first date.