This version of the Emergency Medical Hologram (or EMH) was a corrupted program on board the U.S.S. Equinox. Like the uncorrupted Voyager EMH (as well as the Enterprise E's EMH), this program was portrayed by Robert Picardo in the TV series, Star Trek: Voyager.
He was built into the Equinox ship's systems as a backup EMH, a standard program in Starships incase the ship's Chief Medical Officer (CMO) is deceased. At some point, after the ship was lost in the Delta Quadrant and probably during the Equinox's encounter with the Krowtonan Guard, they lost their CMO and activated this EMH. Sometime after, they encountered an alien race. That race introduced them to another lifeform which they called "Spirits of Good Fortune." Once they discovered from the accidental death of the alien that they could be used as a source of fuel to enhanced their warp core, they told their doctor to help them. The doctor might had initially refused so they deactivated his ethical subrotines, turning him into a monster.
Later on he developed a means to convert the aliens dead bodies into fuel. When Voyager found the ship and discovered their plans, Voyager's EMH during the conflict between the two ships discovered this EMH. Equinox EMH then took Voyager's mobile holo-emitter, locking Voyager EMH in the Euqinox computer. The Equinox EMH acted as a spy and saboteur aboard Voyager, that is until the Voyager EMH returned and deleted this EMH, basically a hologram program's death.
When the Equinox crew attemped to contact their EMH, the Voyager EMH responded to them simply stating "I'm sorry, but your doctor's no longer on call."