The episode introduces a new race of humanoids from the Gamma Quadrant, known as Miradorn. During a business transaction between unscrupulous bar operator Quark and a pair of Miradorn twins, a Mirador visitor attempts to steal a valuable item. Odo intercedes, but not before one of the twins is killed. The assailant, identified as Croden, is taken into Odo's custody while the remaining twin, Ah-kel vows vengeance. Croden makes several comments to Odo regarding Changelings. This piques Odo's interest, as he has never encountered another shape-shifter and all that is known is that he was found near the wormhole.
Croden claims to have met one before. Croden's motives are suspect as he never divulges anything outright, but he claims there were once shape-shifters on his home-world. According to Croden, they were persecuted and driven off the planet; however, he may know of a place where they still exist. Odo is dubious of Croden's stories until Croden gives him a necklace with a stone that changes shape. Bashir examines it curiously and tells Odo that, given its composition, it could be thought of as his cousin.
Commander Sisko and Lt. Dax meanwhile try to contact Croden's home-world. Apparently highly xenophobic, one of their leaders demands Croden's return, to which Sisko acquiesces.
Back on the station, Croden tries to tempt Odo, telling him that though he could in person direct Odo to the colony of changelings he claims to have found. Sisko assigns Odo to return Croden to the latter's homeworld via runabout shuttle. Complicating matters the surviving Miradorn twin, Ah-Kel, has remained docked at Deep Space Nine, meticulously checking each ship that leaves to ensure he doesn't lose his opportunity to exact vengeance on Croden. Masked by a departing freighter, Odo manages to ferry Croden to the Gamma Quadrant undetected, though back on DS9, Ah-Kel quickly intimidates Quark into revealing that Odo has absconded with Croden and Ah-Kel enters pursuit.
In the runabout shuttle with Croden, Odo navigates the Vortex, an asteroid field that Croden informs him is filled with unstable pockets called toh-maire. Odo is forced to release Croden to assist in evading Ah-Kel's ship. Croden is forced to land on the planet he had claimed contained the changeling colony. On the surface, Croden seems overeager, which reignites Odo's doubt. Odo demands the truth of Croden's stories. Croden reveals that though he had heard stories, he had never actually met a changeling. The shapeshifting stone he had shown Odo was bought at a marketplace. Croden uses the stone to open a chamber he had left on the planet's surface, containing his daughter, whom he had put into stasis.
Their life sign's having been detected, Ah-Kel has fired on the surface, prompting the three to return to the ship. A falling rock incapacitates Odo and Croden carries him back to the ship. In the Vortex, Odo tricks Ah-Kel into firing on a pocket of toh-maire, destroying the pursuing ship.
Ultimately, Croden decides to answer for his crime on his homeworld and asks Odo to care for his daughter, but Odo, indebted to Croden, finds a Vulcan ship that agrees to take Croden and his daughter back to Vulcan with it. Croden gives Odo his necklace containing the Changeling stone as a sign of thanks for saving him and his daughter.