H. Dunbar was Henry Starling's assistant at Chronowerx Industries during the late 1990s.
Dunbar helped Starling prepare for his trip back to the future. During Starling's preparation, he attempted to vaporize Rain Robinson, the astronomer who located the USS Voyager in orbit of Earth.
He later transported Starling, who was being held prisoner aboard Voyager, from the Federation starship by using the timeship Aeon in conjunction with Starling's SATCOM 47 satellite.
Soon after, Dunbar created a diversion to distract Tom Paris and Rain Robinson from stopping Starling's flight aboard the Aeon. By leading Paris to believe that the tachyon particle emissions that were being emitted from the tractor trailer he was driving was the Aeon, he drove the otherwise empty truck into the barren California deserts.
Dunbar was eventually killed when Tuvok, B'Elanna Torres, the Doctor and Chakotay destroyed his truck moments before he would have killed Paris and Robinson. He attempted to run the two down but Voyager's shuttle, flown by the others, arrived to help and destroyed the truck with a single phaser blast, killing him. (VOY: "Future's End", "Future's End, Part II")