Stewart was once afflicted with a case of chronic paronychia. In an unrelated incident, his appendix was removed. He has some low-level near-systemic damage, including myelinsheath damage, minor mononeuropathies, and some involvement of dermatomes.
He was the first of several crewmembers who boarded the USS Enterprise when it was pulled into the mirror universe. For the mission, he wore a uniform designed to mimic Starfleet uniforms in the primary universe. He was given limited information about the nature of his assignment, primarily that he was going to visit another Enterprise (that was not his Enterprise) and that he should not speak to anyone. He was then given security codes which would grant him first-level access to steal specific files from the computer core. He was to feed the data to a transmitter, and then wait to be beamed out six hours later. Stewart was apprehended using access station two of the Enterprise's main computer core.
Thinking that he was still dealing with the crew of his Enterprise, Stewart had awkward interactions with the crew of the USS Enterprise. He tried unsuccessfully to bribe security guards Ryder and Mirish into letting him go. He was terrified of being inspected by Beverly Crusher, not wanting to be one of her "guinea pigs." After being checked out in sickbay, he again attempted to escape by offering Deanna Troi sexual favors, boasting that he would be more capable than William T. Riker. He called Worf a slave, which Worf considered "rude."
While discussing the situation after they had established that they were in the 'mirror universe', Worf suggested that 'their' Stewart be sent to the other Enterprise impersonating his counterpart, but Picard rejected that idea as the other Stewart would have lacked the experience to pass himself off in that manner.
The mirror Stewart suddenly sickened and died while on the Enterprise after his blood overloaded with viral organisms. Dr. Crusher discovered that this was pre-planned by Stewart's handlers in the mirror universe - the virus was set to go off at a specific time. This suggested to Crusher that Stewart was intentionally abandoned after collecting and transmitting the Enterprise security codes. (TNG novel: Dark Mirror)
|ISS Enterprise-D personnel|
|Reginald Barclay • Beverly Crusher • Wesley Crusher • Eileen Hessan • Geordi La Forge • Miles O'Brien • Jean-Luc Picard • William T. Riker • Mark Stewart • Deanna Troi • Worf|