Returning to DS9 after a routine mission, Kira and Bashir answer the distress signal of a disabled Kobliad ship.
Turns out it's a prisoner transport ship. And said prisoner, a man named Rao Vantika, perished after setting a fire to attempt an escape.
But this isn't good enough for Rao's pursuer, Ty Kajada. She's been pursuing Rao for twenty years, and she wants every test under the sun done to make sure he's dead as a doornail. Bashir obliges.
Turns out her paranoia is well placed. Rao has perfected a Joker-esque method of cheating death. As revealed when he contacts Quark in a new body. Quark himself is masterminding a theft of valuable deuridium, with a group of mercenaries he has ordered Quark to hire. Ty eavesdrops on Quark and his crew, but gets pushed off a high balcony, winding up in sickbay.
The time of the theft comes, and Rao's new vessel is revealed to be Julian. Transferred to him at the episodes start when he grabbed him by the throat.
After he and his men kill the crew shipping the deuridium, they prepare to make off with it. But new security member Lt. Primmin has stopped their attempt to knock power out and allow them to escape.
After a quick back and forth bantering with Sisko, Jadzia sends a disabling pulse through the tractor beam. Julian beams back aboard, but his act doesn't fool anyone. Sisko quickly stuns him, and wheels him off to sickbay, where the last of Rao's cells are removed and contained.
Ty thanks them for their assistance, and asks if Rao has been transferred into her custody. When confirmed, she vaporizes the containment unit. Ending Rao's existence for good, and taking her leave.
This episode provides examples of:
- Continuity Nod: When talking about ways Rao could have escaped, Bashir mentions and dismisses "Cognitive Brainwave Transfer", because no non-Vulcan has ever managed it
- Crazy-Prepared: According to Kajata, Vantika has faked his death innumerable times in the past, which is why she is so skeptical that he really died on her ship. Considering that he invented a portable brain uploader that he could hide under his fingernail as an emergency escape route, it's not hard to believe.
- Evil Is Hammy: Rao Vantika takes a big bite of Cold Ham when he hijacks Bashir.
- Fair Cop: Ty Kajada
- Freeze-Frame Bonus: As Rao releases Quark, you can just catch a glimpse of Bashir's face.
- Grand Theft Me: A criminal takes over Bashir's body.
- I Know You Know I Know: Sisko explains to Primmin that this is one of Odo's standard tactics, especially with Quark.
- Immortality Seeker: Vantika will do anything to keep himself alive, no matter how insane or destructive to others.
- Jerkass: Primmin comes across as rather arrogant and dismissive of Odo early on, though he does try to make peace with him.
- Jurisdiction Friction: Odo bristles at Starfleet Security officer Primmin's attempt to take over the investigation, and considers resigning. Sisko gives him a Rousing Speech about how no one can do the things Odo can do, that Sisko needs Odo, and states that in joint operations like this, Odo is actually in charge. This mollifies Odo.
- Mad Scientist: Kajada admits some begrudging respect for Vantika's keen scientific mind. Unfortunately, he is also a psychotic murderer who has committed many evils in his obsessive pursuit of immortality.
- Never the Obvious Suspect: When the protagonists start to realise Vantika has transferred his consciousness, Kajada becomes their main suspect, because she would have been the most obvious target for the transfer, and because of a couple of suspicious things she does. But it turns out Dr. Bashir is actually the one Vantika resides in.
- 90% of Your Brain: Dr. Bashir, who really should know better, repeats the old saw that "sentient beings only use a small portion of their brain" as a reason why there's "plenty of room" for Vantika to hide.
- Properly Paranoid: Kajada's paranoia that Vantika is still alive is well justified. Particularly since, as she points out, Vantika was the one who started the fire that "killed" him, and he's not the type to do something like that without a plan.
- Red Herring: There is some evidence that causes the crew to initially suspect Rao has taken over Ty. Towards the end of the episode, Primmin is also presented as a potential suspect.
- Technobabble:Jadzia: I've been asking myself: Why would anyone induct a bioelectrical charge into a glial cell?
Sisko: A question I have always wondered about.
- Why Don't You Just Shoot Him?: Ty vaporizes the container holding Rao's essence, to ensure that he can't Body Surf anymore.
- You Have to Believe Me!: Averted. The crew is understandably skeptical of Kajada's claim that Vantika is somehow alive, with his body sitting in their morgue, but she convinces Sisko to keep investigating anyway.
- You're Insane!: Vantika's helmsman says this when he's ordered to go to warp with a Tractor Beam on them, which would tear the ship apart. Vantika responds by shooting him.