Melanie Jane Bush was a computer programmer. She hailed from Pease Pottage,West Sussex, at the turn of the 21st century. She travelled with the Doctor during his sixthand seventh incarnations. Although she was present for his sixth regeneration, she did not witness it, as she was unconscious at the time.
She had a temporally complex relationship with the Doctor. She met the Doctor in an order different than he met her, as Charley Pollard and River Song later would. Eventually, however, their timelines synchronised, and she had a more-or-less linear relationship to the Doctor, starting in the later period of his sixth incarnation. Her temporal relationship to the Seventh Doctor was considerably more straightforward and linear.
Under the Doctor’s tutelage, Ace fought the Daleks and faced Davros in November 1963. During this adventure, her portable stereo was destroyed by a Dalek. She opposed Helen A and her sadistic government, which required people to be happy on pain of death. She stopped the Cybermen from getting hold of Nemesis in 1988 and saved the Psychic Circuson Segonax from the Gods of Ragnarok. She also met Brigadier Lethbridge-Stewart, helping UNIT defeat the Destroyer and Morgaine in Carbury in 1997.
The circumstances of Ace’s parting of ways with the Doctor are not known, as the series went on hiatus in 1989 with the end of the very next serial, Survival, in which Ace is returned by the Doctor to Perivale but ultimately chooses to leave again with him. A painting seen in the extended version of the serial Silver Nemesis suggests that at some point in her personal future Ace will end up in 18th or 19th Century France. This idea is further explored in the novelisation of The Curse of Fenric and the Virgin New Adventures. The novelisation contains an epilogue not included in the televised serial, in which the Doctor visits an older Ace in 1887 Paris.