Luther Sloan was a Human operative of the clandestine intelligence agency Section 31. In his eyes, to protect what the Federation had worked hard to build, the ends justified the means and he was willing to do almost anything, even cutting ties to his family and friends and violating the Prime Directive.
In 2374, Sloan attempted to recruit Julian Bashir into Section 31's ranks, staging an elaborate deception using a holodeck in an attempt to test Bashir's loyalties. Soon after, Sloan gave Bashir his first "assignment" – 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.
Sloan revisited Deep Space 9 when Bashir convinced Section 31 that he had devised a cure to the morphogenic virus infecting the Founders. Bashir and Miles O'Brien attempted to use Romulan mind probes to extract the information regarding the cure from Sloan's mind. Sloan triggered a lethal implant in his brain, committing suicide, but Bashir and O'Brien were able to prolong his life long enough to get the secret of the cure. Unfortunately, Sloan took the rest of his secrets about Section 31 to the grave with him.