In a fairly routine plot-based mystery, Bashir's attempts to resuscitate the critically injured criminal Vantika fail, and the man dies. Kajada (Caitlin Brown), the security officer escorting the convicted killer to prison, however, is convinced that Vantika's consciousness still exists and may be plotting to hijack a supply of diridium en route to the station.
"The Passenger" provides a workable plot, with few unexpected twists, so the whole thing pretty much rides on the execution. In a word, this execution is "okay." Not much jumps out here, neither favorably nor unfavorably. The script's setup of the "possession" idea is reasonably done, though straining the bounds of typical, established plausibility. The show throws up a decent smokescreen as it hints that Vantika may have transferred his consciousness into Kajada's brain; but it really turns out to be Bashir, who walks around for the first four acts without knowing he's the villain. Once Vantika takes over Bashir, however, the story doesn't deliver the stellar last act it could've. Siddig El Fadil's performance as Vantika is a bit off-kilter, with bizarre line delivery (that is reported to have been over-dubbed in post-production).
The technobabble-heavy solution to overpowering Vantika's personality is unconvincing and dramatically unsatisfying. But most interesting in the show (and in tune with the series' nature of interpersonal conflict) is Odo's friction with Starfleet security officer Primmin (James Lashly), which shows that change never comes easy. One of the best scenes is one between Odo and Sisko, that highlights the commander's calm ability to diffuse tough situations with diplomacy.