DS9 Season 7 Episode 16 Inter Arma Enim Silent Leges

Plot

As Bashir prepares for a conference on Romulus, Section 31 agent Luther Sloan appears with an assignment for him. Captain Sisko advises him to accept it, in order to learn more about the secretive agency.
Bashir is asked to determine whether Koval, the anti-Federation head of the Romulan Tal Shiar intelligence agency and a candidate for the influential Continuing Committee, suffers from Tuvan syndrome, a degenerative disease. Bashir discusses the issue with Admiral William Ross, who says it would be better for the Federation if Senator Cretak were appointed to the committee instead.
Bashir meets Koval at the conference, and later tells Sloan that he believes Koval does have Tuvan syndrome. Sloan asks how the disease could be accelerated. Bashir, suspecting that Sloan is plotting to covertly assassinate Koval, informs Admiral Ross, who plans to have Sloan arrested. Ross muses that Sloan could have an accomplice on Romulus.
Before Sloan can be arrested, Bashir overhears that Ross has suffered an aneurysm. With nowhere else to turn, Bashir tells Cretak of his suspicions about Sloan. Cretak agrees to help Bashir identify Sloan's accomplice by giving him classified Tal Shiar information.
The next day, Koval has Bashir arrested and tortured. Bashir and Cretak are brought before the Continuing Committee, and Bashir tells them about the Section 31 plot against Koval. Koval brings in Sloan, badly beaten, and says Section 31 does not exist; Sloan is merely a renegade Starfleet officer obsessed with getting revenge for his mentor's death. The committee convicts Cretak of treason for planning to share Tal Shiar intelligence with Bashir; Sloan is to be held for further interrogation. Enraged, Sloan grabs a guard's weapon; Koval fires first, apparently vaporizing him.
That night, Bashir demands the truth from Admiral Ross. Off the record, Ross reveals that Koval is secretly working for Starfleet. The real mission was to discredit Cretak, who would abandon the Federation alliance if she thought it in the best interest of the Romulans to do so, and get Koval onto the committee. Sloan was transported away just before he was shot. Bashir is disgusted that the Federation would resort to such machinations.
Back aboard Deep Space Nine, Sloan appears in Bashir's quarters, explaining that he needed a man of conscience for the operation—that the Federation needs men of conscience, but it also needs men like Sloan. Bashir considers reporting Sloan's visit to station security, but decides not to.