A Starfleet ensign aboard Voyager, Mulchaey is attacked in the science laboratory in 2375 by a growing Borg maturation chamber, which samples his genetic material to create the drone called One.
Ensign Mulchaey appears in the fifth-season Voyager episode Drone, played by Todd Babcock. He is on duty when a transporter accident merges the Doctor's twenty-ninth century mobile emitter with some of Seven of Nine's nanoprobes.
Left in the science lab for analysis, the emitter is taken over by the nanoprobes and begins to assimilate the equipment around it. When Mulchaey enters the room, an extraction tubule strikes him in the neck and takes a tissue sample, leaving him unconscious but otherwise unharmed.
The nanoprobes use his DNA as the template for a Borg foetus, which matures within hours into the advanced drone who takes the name One. Mulchaey recovers in sickbay, and is in a biological sense the drone's parent. He is not seen again, though his name is mentioned in several later episodes.