Christopher Pike knew Leland pretty well, although when they met during the red burst investigation, he had not seen Pike since before his hair went grey. (DIS: "Saints of Imperfection") One of his operatives, Philippa Georgiou, claimed that Leland was just a puppet following orders. (DIS: "Light and Shadows")
At one point, Leland was involved in an incident where he was "up to his ass" in alligators on Cestus III. He claimed this to be the reason he transferred to Starfleet Intelligence. (DIS: "Saints of Imperfection")
In the mid-2230s, as a young operative, Leland was involved with the time travel research called the Daedalus Project. In 2236, he worked with Michael Burnham's parents in the project on Doctari Alpha, and blamed himself for their deaths when the Klingons attacked the colony, which claimed their lives. Philippa Georgiou knew that he was responsible for the Burnhams' deaths. (DIS: "Light and Shadows", "The Red Angel")
In 2251, Leland conducted a mission to Deneva that unfortunately involved the wrong ambassador. This incident was kept classified in his secure personnel file, but Georgiou was able to breach the firewall protecting his file to learn this information to later blackmail him to assist the USS Discovery. (DIS: "Saints of Imperfection")
Later on Leland supervised Philippa Georgiou's mission to Qo'noS to shore up L'Rell's regime, and later ferried Ash Tyler and Tenavik to Boreth. Control advised Leland that Tyler would be a strong asset to the organization. Part of Leland's intention had been to recruit Tyler for Section 31, but he left much of that task to Georgiou as well. He told her that she needed to work on her recruitment speech, but she fired back that her speech was just fine and that Tyler was in. (DIS: "Point of Light")
After Spock fled Starbase 5, Captain Leland devoted significant Section 31 resources to find him. (DIS: "The Sound of Thunder") He would eventually capture what would later turn out to be illusory versions of Spock and Michael Burnham created by the Talosians. (DIS: "If Memory Serves")
Following the destruction of Section 31's Headquarters, Leland and the NCIA-93 rendezvoused with the Discovery. Leland briefed the crew on the Daedalus Project and its connection to the Red Angel. After formulating a plan to capture the Red Angel, Leland went to Essof IV along with Discovery. (DIS: "The Red Angel")
While orbiting Essof IV, Control captured Leland, later killing and reanimating his corpse using nanites, taking his identity. Posing as Leland, Control tried to lure Tyler and Georgiou into transferring the Sphere data to the NCIA-93. Georgiou discovered the deception and prevented Control from succeeding. Control then escaped using a shuttlepod. (DIS: "Perpetual Infinity")
Control led a Section 31 fleet to destroy Discovery and the USS Enterprise, but was ultimately killed when Georgiou trapped the rogue AI in a magnetized room, destroying Leland's body. (DIS: "Such Sweet Sorrow", "Such Sweet Sorrow, Part 2")
"Is that gray hair I see?"
"Yeah, well, it's one of the trade-offs of having actual hair."
"There are always lives at stake. That's what keep us employed. See, we do what we do so you can do what you do."
Leland was played by actor Alan van Sprang.
The character first appeared in the "bonus scene" deleted from the season 1 finale "Will You Take My Hand?". In that scene, he was disguised as a Trill and Georgiou was able to deduce that he wasn't. He subsequently dropped his holographic disguise and was responsible for recruiting Emperor Georgiou into the organization.