The mirror-universe counterpart of Charles Tucker, chief engineer of the ISS Enterprise, whose face has been disfigured by years of radiation exposure in the ship's engine room.
The mirror Tucker appears in both parts of In a Mirror Darkly. Years of work beside a badly shielded warp reactor have left one side of his face scarred and one eye clouded, and he is as coarse and suspicious as the rest of the Terran crew.
He installs the Suliban cloaking device that lets Enterprise slip into Tholian space. When the cloak fails he is blamed for sabotage and put in the agony booth by Reed; in fact T'Pol had forced him to do it through a mind meld and wiped the memory.
After the loss of Enterprise he takes charge of the USS Defiant's unfamiliar 23rd-century engines, bringing its systems back to life in time for Archer's attack on the rebels.