Ace

Ace, real name Dorothy (Dorothée) Gale McShane, was a companion of the Seventh Doctor. Like most individuals who travelled with the Doctor prior to his ninth incarnation, she was a human from late 20th century Earth. A native of the London suburb of Perivale, she was born on 20 August, 1970 ("Set Piece," "Relative Dementias," "Timewyrm: Revelation," "Falls the Shadow)".

Biography
Ace was working as a waitress in a bar on Iceworld in the far future when she first met the Doctor. She had been a troubled teen on Earth, having been expelled from school for blowing up the art room as a "creative statement". Gifted in chemistry (despite failing it for her "O"-levels), she was in her room experimenting with the extraction of nitroglycerin from gelignite when a time storm swept her up and transported her to Iceworld, and far in her future. There, she met the Doctor and his companion Mel. When Mel left the Doctor at the conclusion of their battle with Kane, he offered to take Ace with him in the TARDIS, and she happily accepted ("Dragonfire").

Ace was arguably the most independent of all the Doctor's companions up to that point. She had suffered traumatic events in her childhood, including a bad relationship with her mother and the racist firebombing of her friend Manisha's flat. (Manisha died in the firebombing, and Ace in anger set fire to Gabriel Chase, a long abandoned mansion rumored to be haunted by an ancient evil ("Ghost Light," "Blood Heat").) Consequently, Ace covered up her own fears and insecurities with a streetwise, tough exterior. Her weapon of choice, disapproved of by the Doctor (who nonetheless found it useful on occasion), was a powerful explosive she called "Nitro-9", which she mixed up in canisters and carried around in her backpack.

Affectionately giving the Doctor the nickname of "Professor", she was convinced that the Doctor needed her to watch his back, and protected him with a fierce loyalty. In turn, the Doctor seemed to take a special interest in Ace's education, taking her across the universe and often prompting her to figure out explanations for herself rather than giving her all the answers.

Early travels
Under the Doctor's tutelage, Ace fought the Daleks in 1963 ("Remembrance of the Daleks") and the Cybermen ("Silver Nemesis"), encountered the all-powerful Gods of Ragnarok ("The Greatest Show in the Galaxy"), the sadistic torturer called the Kandy Man ("The Happiness Patrol"), and many other dangers. She also faced the ghosts of her own past ("Ghost Light," "The Curse of Fenric"). Over time, she began to mature into a confident young woman, and her brash exterior ceased to be a front.

What the Doctor was aware of but Ace was not, was that her arrival on Iceworld was no accident, but part of a larger scheme conceived by Fenric, an evil that had existed since the beginning of the universe, a plan that stretched across the centuries. Ace was a "Wolf of Fenric", one of many descendants of a Viking tainted with Fenric's genetic instructions to help free it from its ancient prison, and a pawn in the complex game between it and the Doctor. After Fenric was defeated, Ace continued to journey with the Doctor.

Later travels
Indications exist that the Doctor had plans to eventually take Ace to his homeworld of Gallifrey and secure her admission to the Prydon Academy, possibly as part of his assumed mission as "Time's Champion." However, Ace became more and more frustrated with the Doctor's manipulations, eventually leaving his company ("Love and War"). She joined Spacefleet and fought the Daleks for three years, later rejoining the Doctor and his new companion Bernice Summerfield, older and more hardened "(Deceit)." Ace's relationship with Bernice was at first less than cordial, possibly out of jealousy, but the two eventually became friends.

Ace's relationship with the Doctor remained strained for some time, but they eventually resolved their differences. Finally, after their ordeal with the [Ant]]s, Ace left the Doctor again to become Time's Vigilante, using a short-range time hopper mounted on a motorcycle to patrol a particular segment of time; in effect doing what the Doctor does, but on a smaller scale ("Set Piece").

Status
Varying and contradictory reports of Ace's eventual fate exist. She may have been killed sometime before the Seventh Doctor's regeneration into the Eighth ("Ground Zero"). One report even claims she inherited the mantle of the Time Lords when they became extinct ("Death Comes to Time"). Quite possibly this confusion is owing to the existence of an alternate reality containing a young woman, also called Ace, who travels through time in the company of a mystery figure known as "The Professor." Yet another reality is known to exist whose version of Ace, called "Alice," accompanies a time traveller known as "The Dominie."