Marcus 'Mark' McHenry was a male, (mostly) human, Starfleet Officer who served in the late 24th century. He served as the conn officer aboard the USS Excalibur (NCC-26517) and the USS Excalibur (NCC-26517-A).
Mark's great grandmother was Carolyn Palamas, a Starfleet officer who served on the USS Enterprise (NCC-1701) under Captain James T. Kirk in 2267. Palamas was part of a landing party that encountered the Being who claimed to be the Greek God, Apollo. She had a brief relationship with Apollo, which left her pregnant. Palamas sent her infant daughter, Athena, to Earth to be raised by her sister and died soon after of celebium poisoning in 2269.
McHenry was the first male descendant of Apollo, and the first to have any extraordinary abilities. He was born on Inferna Prime in the year 2340 to George and Sheila McHenry. Nicknamed "Sandy" (short for Sandman) by his grandparents. Apollo's brethren, who called themselves the "Beings", immediately sensed something special about him. The Being known as Artemis took an interest in McHenry and visited him on a regular basis, although only McHenry could see or hear her. She called him "Marcus".
When McHenry was eight, an incident with Artemis caused Mark's father to leave and never return. In later years, upon McHenry reaching puberty, McHenry and Artemis' relationship would become a physical one.
McHenry angered Artemis in the year 2357 when he rejected her plan to make him an "Ambassador" of sorts between the United Federation of Planets and the God-like Beings, choosing instead to join Starfleet Academy. McHenry barely escaped Artemis' wrath with his life.
McHenry entered Starfleet Academy in the year 2357. McHenry's squad consisted of himself and cadets Soleta of Vulcan, Zak Kebron of Brikar, Tania Tobias of Earth, and Starfleets first Klingon recruit, cadet Worf.
McHenry's heritage gave him an uncanny grasp of navigation and Stellar Cartography. In class, he would seem to be barely paying attention to the instructor, but would then be able to answer her complex questions right off the top of his head without the use of, indeed faster than, a computer. McHenry also had the ability to sense his whereabouts anywhere in the galaxy, without then use of instruments. He could also sense the slightest alteration of a ship's heading.