Name: Unknown; generally went by the name Beatrix ‘Trix’ MacMillan while travelling with The Doctor, although she was referred to as Patricia Joanne Pullman on one occasion and a call to her mother suggested that her real surname was MacAlister
Time of Origin: Earth, apparently the present (Although her involvement with Sabbath when The Doctor first met her leaves this open to debate)
Time Span: Technically started travelling in the TARDIS in “Time Zero”, but her presence was only discovered by the others at the conclusions of “The Last Resort”; subsequently remained as a full-time companion until “The Gallifrey Chronicles”
Doctor: Eighth Doctor.
Fellow Companions: Fitz Kreiner, Anji Kapoor, K9, implied that she met The Brigadier.
The details of Trix’s life before becoming involved with The Doctor have never been made clear, with even such details as her real name and country of origin being a mystery (Although this is partly due to the fact that Sabbath’s role in her presence when she and The Doctor first met raises certain questions about where she originally came from). However, what is known for certain is that she was a con artist, possibly involved in sex work at some point. In ”The Gallifrey Chronicles” she at one point evades arrest by police, who know her by the name “Patricia Joanne Pullman” and are seeking her for the murder of Anthony Charles Macmillan (suggesting that the name she uses while travelling in the TARDIS is an alias).
When she first met The Doctor, she was posing as a descendant of Tsar Nicholas II, a role that The Doctor’s then-nemesis Sabbath had hired her to play. At the end of the novel, she stowed away in the TARDIS without The Doctor’s knowledge, making brief appearances in some subsequent stories – mostly to provide advice and information to others who had somehow become lost inside the ship, preferring to remain inside due to the TARDIS representing the only ‘stable point’ in the increasingly uncertain universe created by Sabbath’s actions – but managing to avoid detection by The Doctor and his companions until “Timeless”. Despite the unorthodox manner of her arrival, The Doctor apparently eventually came to accept her presence on the ship, recognising the value of her skills at disguise on more than one occasion and trusting her to do the right thing when it counted.
Possessing several character flaws and fleeing her unpleasant past, Trix is among The Doctor’s more troubled companions. She was initially rather materialistic – a trait which causes particular problems in ”Emotional Chemistry” when she sought to steal a valuable locket rather than contact The Doctor for help – as well as deceptive. Although her expertise in the art of disguise has proved useful at several points in her adventures with The Doctor – such as when he had her infiltrate the Tower of London prior to the Battle of Bosworth Field in “Sometime Never…” – it also left her vulnerable to the allure of an alien that offered her the ability to remake her body at will in ”Halflife”. Despite this she often demonstrated a significant amount of compassion for the people she met in her travels, most notably in “Sometime Never” when she befriended the princes Richard and Henry the day before history recorded that they would be found dead, requesting that they call her ‘Aunt Beatrice’ and telling them a modified version of Cinderella to comfort them on what could be their last day alive. On another occasion she gave a man a winning lottery ticket from the future as compensation for his recent troubles when he became caught up in the schemes of Sabbath’s allies (“Timeless”).
Although her disguise expertise proved of vital assistance to The Doctor on several occasions, it also left her vulnerable to some outside influence, such as when an alien offered her the ability to rewrite her body at will despite the fact that this would require her to act as a host for the life-form in question (“Halflife”). Her knack for disguise was explained as a result of her not wanting to feel conspicuous, an attitude that was further reflected by Trix showing discomfort when dealing with physical injuries, and apparently trying to forget some unspecified accident that befell her father.
Although excited at the opportunities travel in the TARDIS offered her, Trix was never a selfish woman, offering comfort and advice to temporary visitors to the ship even when she was hiding from The Doctor during her initial time in the TARDIS (“Reckless Engineering”, “The Last Resort”), causing her to feel insulted when The Doctor asked her why she’d help him deal with a problem when there was no profit in it (Although this hostility was later revealed to have been prompted by The Doctor’s contact with a ‘ghost’ being generated by an alien ship rather than his own feelings about Trix’s presence) (“The Deadstone Memorial”).
In ”The Gallifrey Chronicles” it was revealed that she had been collaborating with The Doctor’s former companion Anji Kapoor (who left the TARDIS shortly after Trix was discovered), passing Anji information about the future on her returns to contemporary Earth in the form of copies of future issues of the Financial Times, thus enabling Anji to invest accordingly in her job as a stockbroker. Also in that novel, she began a romantic relationship with her fellow companion Fitz Kreiner, and the pair made plans to stop travelling with The Doctor and settle for a while on contemporary Earth using some of the proceeds acquired by Trix’s partnership with Anji. However, the novel ended before revealing whether They eventually went through with this plan, the conclusion showing Trix and Fitz accompanying The Doctor as he jumped into the mountain headquarters of the alien race known as the Voreat present, the most likely conclusion is that she and Fitz survived and subsequently parted company with the Eighth Doctor as he left to restore his formerly missing memories, most likely retaining the now-returned K9 Mark II – given his absence from the Ninth Doctor’s life – as a housewarming present.