Luther Sloan was a 24th century Human operative of the clandestine intelligence agency Section 31. Although he and the rest of Section 31 claimed to operate independently of both the United Federation of Planets and Starfleet, performing actions most Federation citizens would abhor and otherwise consider morally questionable, he saw himself as doing what was necessary to protect their interests. In his eyes, to protect what the Federation had worked hard to build, the ends justified the means. So great was his dedication to protecting and preserving the Federation that he was willing to do almost anything, even cutting ties to his family and friends and violating the Prime Directive.
Sloan wanted to be a medical doctor in his youth, so he was glad to see his son enter Starfleet and accomplish the goal. Unfortunately, during the Dominion War his son's convoy dropped out of warp to rendezvous with a Klingon Bird-of-Prey, only to find three Dominion attack ships waiting for them instead. He was killed in the subsequent battle. (DS9: "Inquisition")
Sloan once described himself as "a man of secrets", who had to live in a world of mystery and deceit once he joined Section 31. His wife Jessica and their children lived on Earth, but Sloan's clandestine missions meant he almost never saw them. Luther knew this made the marriage "a living hell" for Jessica, but he was so dedicated to the preservation of the Federation that he saw it as a necessary sacrifice.
Despite his determination, Sloan's actions often weighed heavily on his conscience. He was unable to sleep at night, though he took comfort in knowing that citizens of the Federation were able to do so. Ultimately, he died wishing he could apologize for cheating his family out of being in his life – and for cheating himself. Because he had spent his life erasing any trace of his actions, it was as if he had never existed. (DS9: "Extreme Measures")
Interest in Bashir
In 2374, Sloan attempted to recruit the genetically-engineered chief medical officer of Deep Space 9 into Section 31's ranks, staging an elaborate deception using a holodeck in an attempt to test Bashir's loyalties. In this scenario, Sloan posed as Deputy Director of Internal Affairs, claiming that there was a security leak aboard Deep Space 9. Accusing Bashir of having been recruited as a mole by the Dominion during Bashir's incarceration at Internment Camp 371, Sloan claimed to have had a son who had been killed by the Dominion, and stated that he believed his son's death had been a direct result of information supplied to the Dominion by Bashir. Bashir eventually realized that he was being deceived, and Sloan was forced to terminate the program. Despite this, Sloan expressed to Bashir that he had passed the test, and Sloan was no longer in doubt of Bashir's loyalty. Sloan subsequently offered him a position within Section 31, citing his genetically-engineered background and fascination with spy stories. Bashir ultimately declined the invitation, stating that he did not believe it was proper for an organization such as Section 31 to have such power, acting autonomously and free of any oversight. Detailing his experience with Sloan to Captain Sisko, Bashir expressed his surprise that Starfleet would have such a department. In an attempt to further investigate Sloan and Section 31, Sisko ordered Bashir to accept Sloan's invitation to join the next time Sloan made contact with him. (DS9: "Inquisition")
Sloan returned, the next year, to Deep Space 9, to give Bashir his first "assignment". Although Bashir had refused to join, Sloan claimed that he had been "accepted" into the organization and thus was needed to fulfill his "duties". Sloan goaded Bashir into joining the operation by appealing to Bashir's love of fictional spy dramas and intrigue, stating that he was a man of mystery made for the job he was about to assign him. He instructed him to perform observations of various members of the Romulan government during an upcoming Federation-Romulan conference on Romulus, and in particular Koval, the chairman of the Tal Shiar.
At the conference, Sloan posed as Wendell Greer, a representative from the Federation Department of Cartography. Through a complex series of events, Sloan convinced Bashir that he was planning to assassinate Chairman Koval. Sloan hoped that Bashir's sense of ethics would force him to try to alert the Romulans to Sloan's apparent threat. Bashir approached Senator Cretak, who agreed to break into Koval's personal database in an attempt to find evidence that would reveal Sloan's threat. Cretak was caught while trying to access the classified files and brought before the Continuing Committee, where she was censured for her improper and possibly treasonous behavior.
Ultimately, the entire operation was revealed to be a ruse aimed at getting Koval – a Section 31 mole – elevated to the Continuing Committee. In addition, Admiral William Ross was revealed to be involved in the operation, working alongside Sloan. At the end of the conference, Sloan thanked Bashir for his sense of ethics and for doing "the right thing," while at the same time pointing out that Section 31 existed precisely to protect people like Bashir. (DS9: "Inter Arma Enim Silent Leges")
Morphogenic virus and the Dominion
Several months later, while investigating a cure for the morphogenic virus that had infected Odo along with all the Changelings in the Great Link, Bashir came to the conclusion that the disease had been engineered by Section 31 as a way to attack the Founders and end the threat of the Dominion. (DS9: "When It Rains...") Bashir and his friend Miles O'Brien devised an elaborate scheme to lure Sloan to the station with the hopes of forcing him to reveal the cure to the disease. Bashir informed Starfleet Medical that he had devised a cure to the virus, knowing that Section 31 would send an operative to destroy that information in order to prevent it from falling into the hands of the Dominion. (DS9: "Tacking Into the Wind")
When Sloan boarded Deep Space 9, Bashir stunned him and attempted to use Romulan mind probes to extract the information regarding the cure from Sloan's mind. Ironically, Bashir and O'Brien, supported by Captain Sisko, resorted to the same kind of morally questionable practices that they accused Sloan of. During the procedure, Sloan triggered a lethal implant in his brain, committing suicide to prevent Bashir from finding the cure to the morphogenic virus. Bashir managed to prolong Sloan's life, but the implant had scrambled the operative's neural pathways and brain death was inevitable within an hour. Desperate, Bashir and O'Brien used a neural interface to link their minds with Sloan's in a last-ditch attempt to discover the information. Sloan attempted to distract the intruders with images of his wife, Jessica, his family, and an alter ego who professed to want to reveal the information but somehow was prevented from doing so.
Sloan's alter ego thanked Bashir for having set him free like that, for having showed him that ideology is a poor substitute for kindness and decency. He was about to hand Bashir the solution to a cure for the disease when suddenly Sloan's other side emerged: the Section 31 operative and devoted Federation citizen. He shot the alter ego in an attempt to prevent the information from reaching Bashir, and, before they knew it, Bashir and O'Brien were finding themselves amid the ethical battle that had ensued inside of Sloan's mind. After dragging them through a maze, Bashir was finally able to access the information he needed buried away inside a mental recreation of Sloan's office. But Sloan had one last trap planned for Bashir; with the secret of the cure revealed, Sloan offered to share with Bashir all of his secrets – enough information to bring down Section 31 entirely. This was the one thing Sloan knew Bashir could not resist, and the doctor was nearly trapped in Sloan's mind as their time grew short. Fortunately, O'Brien convinced him to leave in time. Although the secret of the cure to the morphogenic virus had been revealed, Sloan took the rest of his secrets about Section 31 to the grave with him. (DS9: "Extreme Measures")
"How many lives do you suppose you've saved in your medical career?"
"What has that got to do with anything?"
"Hundreds? Thousands? Do you suppose those people give a damn that you lied to Starfleet Medical [about being genetically enhanced]? I doubt it. We deal with threats to the Federation that jeopardize its very survival. If you knew how many lives we've saved, I think you'd agree that the ends do justify the means."
"The Federation needs men like you, doctor. Men of conscience. Men of principle. Men who can sleep at night… You're also the reason Section 31 exists – someone has to protect men like you from a universe that doesn't share your sense of right and wrong."
"Doctor, you've been a beacon of light to me. You're living proof that ideology is a poor substitute for kindness and decency – and that, at the end of the day, it's our actions and not our beliefs that define who we are, what we are."
Much about the man known as Sloan remains unknown, and what is known is shrouded in mystery. If one looks closely, one might discover hints of his real life. For example, while testing Bashir on the holodeck in their first encounter, Sloan claimed that his son, whose name was never revealed, had been killed in a surprise Jem'Hadar attack. In the simulation, this was indicated to be why Sloan thought Bashir was a Dominion spy; while the mention of Sloan's son may have been a ruse to make the simulation even more believable, it may have been based on Sloan's personal life. If the story was true, it may have influenced Sloan's decision to interrogate Bashir in the first place. This would also have given Sloan a personal motive to ensure that the morphogenic virus eliminated the Founders.
Similarly, Koval's story about how Sloan came to work for Section 31 may not be entirely false. In Koval's version of events, after using the mind probe on Sloan, he discovered that Sloan had been the protege of Admiral Fujisaki, whose death was officially attributed to food poisoning. Sloan allegedly became convinced that the Tal Shiar murdered Fujisaki, and he created Section 31 as a means by which he could exact revenge. The true nature of the relationship Sloan had with Fujisaki (if any) is unknown, but the idea of Sloan creating Section 31, which has been shown to have existed in the 22nd century is obviously false.
The factual basis for information revealed while Bashir and O'Brien were inside Sloan's mind is also unclear. It is likely that Sloan, who was dying at the time, simply used elements of his own life to stall for time; it is plausible that he never had a wife or the other family ties he described. Among the things that may or may not be true is Sloan's claim that he once considered becoming a doctor.
Sloan was played by William Sadler.
Sloan and Section 31 epitomize and were products of Deep Space Nine's vision of a more realistic universe in which "paradise" has started to crumble and where the Federation struggles to maintain its high ideals amid difficult situations.
Sadler commented: "I thought of [Sloan] as an Ollie North character. He does what needs to be done, what he feels needs to be done. He breaks all the rules, all the rules of the Federation, in order to keep the Federation safe, or so he thinks and deeply believes. It’s that same argument that went down with the Iran-Contra affair and Ollie North. You do what needs to be done and somebody's got to do it. I remember thinking, 'How freaking cool is it that the Federation, this honorable group, these honorable people for all these years, had this little worm in there who's been changing history for decades.'" 
Despite not directly featuring in DS9: "When It Rains...", Sloan was referred to several times in that episode's first draft script. Bashir and O'Brien started to suspect he had run a burn-back on them after they managed to trace it to the Department of Cartography at Federation Headquarters, also discovering that the culprit had the screen name "W.G.", which Bashir believed stood for "Wendell Greer". Moments after the burn-back caused their consoles to short out, the pair agreed that, if Sloan had indeed done the burn-back, he now knew, much to his dissatisfaction, that they knew everything about the Section 31 conspiracy to create the morphogenic virus that was currently inflicting the Changelings.
While Sloan appeared to bear the rank of a fleet captain while posing as an officer with Starfleet Internal Affairs, it is possible that he truly did hold this rank.
Sloan appears briefly at the end of the The Lost Era novel Catalyst of Sorrows. The novel is set in 2360, although it does not say if he is a member of Section 31 at that point. Sloan also appears in Hollow Men, and makes a brief appearance at the beginning of the Star Trek: Voyager Section 31 novel Shadow.
His mirror universe counterpart is depicted as a member of the Terran Rebellion on Terok Nor fighting under Miles "Smiley" O'Brien against the Klingon-Cardassian Alliance in the novella Saturn's Children and the novels The Soul Key and Rise Like Lions.
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