For the regular universe counterpart, see Mark McHenry.

In the mirror universe, Marcus "Mark" McHenry was a Human/Being hybrid (as he has knowledge of other universes, the ability to project his mind into other universes, his body produces bioenergy that can power a warship and an enhanced brain and intelligence level) that was "recruited" into a Thallonian secret project headed by Lord Si Cwan that was attempting to find the ultimate power source for their brand new warship; the Stinger. McHenry was compatible for the link and became a living computer system and power supply for the ship while being held in stasis in a null sphere. McHenry appeared to be in a constant medically-induced coma and Si Cwan believed himself to be in control; when, in fact, McHenry was well aware of his surroundings and was running every system on the ship and only "allowing" Cwan to use "his" ship. McHenry kept himself entertained by visiting other universes (such as the primary universe).

All this changed when M'k'n'zy of Calhoun and Soleta; teamed up with Elizabeth Shelby, Robin Lefler and Kalinda Si Cwan to commandeer the ship following the exposure of a Thallonian plot to gain power. Soleta used her own telepathic abilities to draw McHenry's mind back from his journey and convinced him to force Cwan and his crew off the ship; then M'k'n'zy took over and ordered McHenry to destroy their escape pods and launch and orbital bombardment on Danteri. Though instinctively loyal to M'k'n'zy to the point he needed his permission to cease the attack, Soleta and McHenry then forced M'k'n'zy into a vision that showed him what McHenry saw; M'k'n'zy's counterpart; Mackenzie Calhoun, a respected and liked commander of his crew (including their own counterparts, along with Shelby's, and Lefler's); this forced M'k'n'zy to order McHenry to cease the attack.

McHenry then joined the Terran Rebellion with the rest of his group; however he willingly chose to stay in the sphere to power the ship, as he "felt safe" there. (NF short story: "Cutting Ties")