Dulmur was an agent of the Department of Temporal Investigations in the 24th century. In 2373, along with his partner, Lucsly, he visited station Deep Space 9 to debrief Benjamin Sisko on a recent time travel incident, wherein Klingon spy Arne Darvin utilized the Orb of Time to take the USS Defiant back in time to 2268 in an attempt to assassinate James T. Kirk.
Dulmur and Lucsly showed no signs of either having senses of humor; indeed, they both claimed to hate jokes.
After the interview, Dulmur told Sisko that he did not believe that Sisko and crew committed any major violations of time travel regulations. Indeed, Dulmur hinted that he himself probably would have expressed his admiration to Kirk, just as Sisko had done. (DS9: "Trials and Tribble-ations")
Dulmur was played by Jack Blessing.
Dulmur's name was intended to be an anagram of The X-Files FBI Special Agent Fox Mulder's last name (Star Trek Encyclopedia (4th ed., vol. 1, p. 223)), though the "e" is substituted for a "u". The Star Trek Customizable Card Game gives his name as "Dulmer", the correct anagram of "Mulder".
The Star Trek Encyclopedia (4th ed., vol. 1, p. 223) identified Dulmer as an agent of the Department of Temporal Investigations.
In the Star Trek Online novel The Needs of the Many, at some point Dulmur contracts a time-related mental illness, and as a result has memories of numerous historical events which "never happened," including an "alternate reality" where Vulcan was destroyed in the 2250s, as well as one where a large-scale Borg attack in the early 2380s nearly destroyed the Alpha Quadrant (firmly placing the frequently inconsistent STO and Star Trek: Destiny series in separate timelines), and is institutionalized as a result. However, his psychiatric nurse, very much intrigued by his actual experience of many different universes, is Q. The novel gives his name as "Wolf Dulmer".
Watching the Clock gives his name as "Marion Frances Dulmur". It takes place in a different timeline from STO, where Dulmur has not contracted the illness that his STO counterpart had. The novel also reveals how Dulmur joined the DTI, having originally been a detective before a suspect escaped due to a temporal anomaly caused by an experiment. This prompted him to track down the scientist responsible, impressing the DTI with his dedication. He once had a wife named Megumi (β), whom he planned to start a family with, but work got in the way and they eventually divorced.