Star Trek: 10 Times Chief O'Brien Suffered
5. Empok Nor
Empok Nor ranks as one of the darkest episodes of Star Trek to that point. Due to an infection with a drug, Garak is possessed of a need to slaughter several Starfleet engineers while aboard the derelict Cardassian station, Empok Nor. Leading the team is O'Brien.
The first pass of the script didn't feature much of a story, bar the actions that Garak commits. Writer Hans Beimler recalled that no one was particularly happy with that draft, as there was no substance to the story. He went back and in the second draft, added a far deeper relationship between Garak and O'Brien.
The episode would bring O'Brien's actions during the Setlick III massacre back to the fore, with the hatred of Cardassians - introduced in TNG's The Wounded - questioned again by the deranged Garak. While attempting to keep his crew alive, O'Brien is forced to relive the horrors of the Cardassian war - all the while dodging the hunt.
The episode's close offers a meditation on PTSD and grief. Though Garak was not responsible for his actions, he speaks to O'Brien about the grief he feels. O'Brien simply reminds him that he will have to live with it now.