The station has been temporarily evacuated because of a Space Thing.
O’Brien and Odo find Quark suspiciously loitering in an airlock.
A cargo ship approaches DS9 and requests assistance. The new arrivals are a polite but nervous male Trill, his bumpy-foreheaded girlfriend, and two Klingon thugs. They force Odo into a box, order Bashir to put the box into a stasis chamber, and then take over Ops.
Quark apparently believed he was arranging a sale with one of the Klingons, but Dax figures it out. Verad intends to steal the 300-year-old symbiont currently joined with the young woman Jadzia to form the unique entity Jadzia Dax.
According to Dax, only about one in ten Trill are selected to be joined with symbionts, and there’s nothing shameful about not being “one of the lucky ones,” but Vered has made his mind up. Ssko reasons that Verad wants to escape through the wormhole after he’s joined. He shoots O’Brien in the shoulder in order to force Bashir to perform the operation.
Sisko works on Verad’s girlfriend Mareel, telling her that Verad will be different after the joining. And in fact, when new joined entity Verad Dax enters, he is walking tall and eager to bond with Sisko about their shared experiences with Curzon Dax.
As Sisko predicted, Verad Dax is cold to Mareel, whom he longer needs. She admits to Sisko that she realizes he’s planning to abandon her.
Quark attempts to redeem himself by attacking one of the Klingon thugs. The distraction gives Bashir the chance to overpower the other thug, and Quark helps save the day by using his lock-picking skills to free Odo.
Sisko gets Mareel to realize that he can restore Jadzia Dax and she can get Verad back if they work together.
While we can be pretty confident all the main characters will be back in next week’s episode, we don’t know what will happen to the guest stars, and the script does a good job turning this uncertainty into the story.
Because we just saw joyful reunions as the evacuated station is repopulated at the end of s1e3 “The Siege,” it’s awkward to have this episode begin with the station re-evacuated (and Quark yet again left behind). After the three-part Season Two Opener (which built organically on the Season One finale, making a coherent, action-packed four-part narrative arc), this stand-alone episode is a low-budget letdown, but it’s polished and helps flesh out the Trill backstory and puts Quark to good use. Dax’s performance was a bit bland, but overall the episode was much better than the average second season episode of TNG.