At a time when Deep Space Nine is all but empty, an unjoined Trill named Verad and his crew (a pair of Klingon mercenaries and a former prostitute) overpower the crew of the station. The Trill, Verad, applied to be "joined" and was rejected; now he wants the Dax symbiont. Forcing Odo into a container and taking the rest of the crew hostage, he makes Bashir to transfer the symbiont into his body, which will kill Jadzia within hours.
Bashir has one of the Klingons act as a nurse as he tries to save Jadzia's life. Meanwhile, Sisko tries to coax his old friend (Verad now has the memories of both Jadzia and Curzon Dax) into setting things right, but he realizes Verad intends to let Jadzia die. Verad's lover begins to realize how much Verad has changed since the symbiont was transferred and begins to think the transfer may have been a bad idea. However, she remains loyal to him.
Quark, who is responsible for Verad and his crew boarding the station, pretends to be injured so Bashir can knock one of the Klingons out. He then cracks the lock on the container Odo is in. Once Verad realizes what has happened, he heads for his ship and takes Kira as a hostage.
By the time Verad reaches his ship, Odo has released the docking clamps, leaving him stranded. Kira overpowers the Klingon who is holding her but in the confusion Verad slips away, heading for a runabout. In the mean time his lover has realized that the man she loves truly is gone and decided to help Sisko. Sisko meets Verad at the airlock to the runabout and the two have a stand off. Believing that Sisko will not shoot his old friend, Verad begins to walk away, but Sisko shoots him, declaring, "Don't call me Benjamin." The Dax symbiont is transferred back to Jadzia.