Within the series’ narrative, the Doctor is a centuries-old Time Lord alien from the planet Gallifrey who travels in time and space in his TARDIS, frequently with companions. At the end of life, the Doctor can regenerate his body; in doing so, his physical appearance and personality change.
The transformation into the Second Doctor (originally referred to as a “renewal”), a figure who was the same ‘essential’ character as the first but with a very different persona, was a turning point in the evolution of the series, and eventually became a critical element of the series’ longevity.
The First Doctor grew progressively weaker while battling the Cybermen during the events of The Tenth Planet (1966) and eventually collapsed, seemingly from old age. His body renewed itself and transformed into the Second Doctor. Initially, the relationship between the Second Doctor and his predecessor was unclear. In his first story, the Second Doctor referred to his predecessor in the third person as if he were a completely different person. His companions Ben and Polly are at first unsure how to treat him and it is only when a Dalek recognises him that they accept that he is the Doctor.
In the second story, The Highlanders (1966–67), Jamie McCrimmon joined the TARDIS crew, and remained with the Second Doctor for the rest of his travels. Ben and Polly left together when the TARDIS landed at Gatwick Airport on the same day they originally left with the First Doctor, after they had stopped the mass kidnapping of tourists by shape shifting aliens. The Doctor and Jamie then became involved in a plot by the Daleks to gain both the “Human and Dalek Factors” when the TARDIS was stolen, which led to them meeting Victoria Waterfield in the 19th century. Victoria chose to accompany the Doctor and Jamie on their travels. Although she felt great affection for the Doctor and Jamie, she was never able to completely come to terms with life in the TARDIS and the constant danger that resulted. She eventually chose to leave after the events of Fury from the Deep (1968) and was adopted by someone in the 20th Century. The Doctor was then joined by Zoe Heriot, an extremely intelligent woman from the 21st century, who helped defeat the Cybermen attack on a space station known as the Wheel. She then stowed away in the TARDIS and, despite the Doctor’s warnings about what she might encounter, chose to remain.
During his second incarnation, the Doctor confronted familiar foes such as the Daleks and the Cybermen, as well as new enemies such as the Great Intelligence and the Ice Warriors. It was during this time that he first met Alistair Gordon Lethbridge-Stewart, in the tunnels of the London Underground. Following the defeat of the Great Intelligence, Lethbridge-Stewart was promoted to Brigadier and became the leader of the British contingent of UNIT, a military organisation tasked to investigate and defend the world from extraterrestrial threats.
The Second Doctor’s time came to an end when the TARDIS landed in the middle of a warzone, created by a race of alien warlords who, with the help of another renegade Time Lord the War Chief, progressively kidnapped and brainwashed humans into becoming soldiers for them, hoping to use the ones who survived to conquer the Galaxy. Although the Doctor was able to defeat their plan, he realised he would be unable to return the human subjects to their various original points in Earth’s history. He therefore contacted the Time Lords, sacrificing his own freedom in the process. He was put on trial by the Time Lords, for breaking their laws of non-interference and was sentenced to exile on 20th century Earth. The Time Lords forced his regeneration into the Third Doctor. Jamie and Zoe were returned to their own time, with their memories of all but their first encounter with the Doctor wiped and the secret of the TARDIS was also taken from the Doctor.
Season 4 (1966-1967)
Season 5 (1967-1968)
Season 6 (1968-1969)
Followed by the Third Doctor