In the events of the 2006 series Christmas episode "The Runaway Bride", Donna Noble is a temporary secretary at H.C. Clements in London, a security firm which, unknown to her, provided a front for the Torchwood Institute up until its collapse following the events of Doomsday, and was then taken over by an alien intelligence. Little is known about her family or past life. Her parents are Geoff and Sylvia Noble

On Christmas Eve, the day of her wedding, she was accidentally pulled into the TARDIS as a result of being dosed withHuon particles by her duplicitous fiancé, Lance Bennett, who was following the orders of the Empress of the Racnoss. She aided the Doctor in defeating theRacnoss Empress, but declined his invitation to travel with him — she was frightened not only by his adventures, but also, to a certain extent, by the Doctor himself. Having seen him commit genocide on the Racnoss, as a parting shot she urged him to find a new companion to act as his moral compass. It was revealed ina later episode that if not for Donna's involvement, the Doctor would have been killed while stopping the Racnoss.

Reappearing in April 2008's series four premiere, "Partners in Crime", Donna had become dissatisfied with regular life and more interested in the bigger picture. She regretted declining the Doctor's offer and had been investigating unusual phenomena in the hopes of finding the Doctor for some time. When investigating Miss Foster and Adipose Industries, the Londoner and the Time Lord were finally re-united. She expressed her regret of not joining him to the Doctor and after stopping Foster's plans to convert the whole of London into Adipose children she joined him in the TARDIS as a regular companion. She made it explicit, however, that she has no romantic attachment to him as Martha Jones and Rose Tyler did.

In "The Fires of Pompeii", Donna continually argued with the Doctor over the moral issue of whether or not he should save the inhabitants of Pompeii from the eruption of Mount Vesuvius the next day. Ultimately, they were forced to cause the eruption to happen, weighing the destruction of the city against the fate of the whole world. When they escaped in the TARDIS and left behind a Pompeiian family they had befriended beforehand, Donna eventually managed to persuade the Doctor to save the family. The Doctor later admitted to Donna that she was right about his needing someone, after which he welcomed her aboard

Donna is the Doctor's full time companion for all 13 episodes of Series 4. Her return to the series sees her with her maternal grandfather, recurring character, as well as her mother, Sylvia. Donna has encountered the Adipose, the Ood, the Sontarans, The Hath, Vespiforms, Agatha Christie and the Vashta Nerada.

(Article thanks to Admiral Mudd)