DS9 Season 6 Episode 18 Inquisition

Plot

One evening, Dr. Bashir treats Chief O'Brien's dislocated shoulder. The next morning, Deep Space Nine is visited by Luther Sloan, an agent from Starfleet Internal Affairs. Sloan suspects that one of DS9's senior staff is a Dominion spy; he confines them to quarters and tells them to await interrogation. At Bashir's interview, Sloan treats him cordially while asking a few light questions. Later, O'Brien tells Bashir that his own interrogation with Sloan lasted hours and focused on Bashir.
Bashir is brought back to the now hostile Sloan, who points out events from Bashir's past that seem to indicate disloyalty or dishonesty. Sloan proposes that, when Bashir was imprisoned by the Dominion the previous year, he was persuaded to become a Dominion spy but repressed his memories of the choice, allowing him to believe he was a loyal Starfleet officer. Bashir refuses to accept Sloan's theory, but Sloan has him detained. Captain Sisko attends Bashir's next interrogation, pointing out holes in Sloan's arguments, but privately suggests to Bashir that Sloan's theories are plausible.
The next day, Bashir is beamed to a Dominion ship, where he is greeted warmly by the Dominion representative Weyoun. Weyoun tells Bashir he made a moral choice to help the Dominion in order to end the war quickly. Bashir, wondering why Weyoun and Sloan are trying to convince him of the same thing, concludes that Sloan is the traitor.
Bashir is rescued by the DS9 crew, but they refuse to listen to his claim of innocence. Desperate, Bashir grabs O'Brien, who pulls his arm away. Bashir, suspicious that O'Brien's injury has apparently already healed, tricks him into revealing he is unaware of the cause of the injury. Bashir realizes he has been in a holodeck simulation since the previous morning.
Sloan ends the simulation and informs Bashir that his loyalty was being tested. Sloan explains that he is a member of Section 31, a secretive autonomous intelligence agency. Bashir questions the legality and ethics of the operation, but Sloan justifies their actions as necessary to protect the Federation. He attempts to recruit Bashir, but Bashir refuses and threatens to expose them.
On DS9, Sisko reports that Starfleet Command neither confirms nor denies Section 31's existence. He predicts that Sloan will try to recruit Bashir again, and orders him to accept, so they can learn more.