When the producers of Doctor Who decided to kill off new companion Katarina, the writer of the serial in which she was to make her swan song was given the task of quickly introducing a new companion to take her place for the remainder of the story. That story was The Daleks' Master Plan, a twelve-part epic by the Daleks' original creator, Terry Nation. Nation had big plans for his creations; buoyed by their popularity, he pitched a pilot to American TV networks. When nobody bit and the pilot remained unproduced, he dusted off and reworked some of the concepts from it for use in this Doctor Who story, including one of the heroes of the original piece, Space Security Service agent Sara Kingdom.
Sara's tenure on the show was short-lived - nine episodes, all contained within one story. When she meets the Doctor she's convinced that he and Steven are criminals; she's been told so by her boss, Mavic Chen, the Guardian of the Solar System (unbeknownst to Sara, he himself is secretly in league with the Daleks). What's more, he convinces her that her brother, Bret Vyon, is a traitor; when Sara next encounters Bret, she shoots him dead without giving him a chance to explain. Bit rash, that. An accident with an interplanetary transporter sends Sara off with the Doctor and Steven; she learns that she's in the wrong and that her brother was innocent. Whoopsie. To make things right, she joins the TARDIS crew in their attempt to stop the Daleks' evil scheme.
The Doctor steals some components from the Monk's TARDIS, and he's able to finally (twelve episodes in) get them where they need to go. Sara helps the Doctor steal the Daleks' time destructor, a devastating weapon. Not knowing Sara would disobey his instructions to seek shelter in the TARDIS, the Doctor activates it - it destroys the Daleks, but also ages Sara to dust.
Of course, as we learned with Katarina, death is never the end for a Doctor Who companion - not when there's
In fact, thanks to Terry Nation, Sara was having her own spin-off adventures decades before devoted fans would make it the norm. In 1966, Nation repurposed more of his discarded Dalek pilot into The Dalek Outer Space Book, featuring stories of the Space Security Service versus the Daleks - including a short comic featuring our heroine.
Don't fuck with Sara Kingdom, boys. She kills Daleks for a living, she's not going to be bothered by a couple of thin-headed hoodlums.
Sara was a great companion; it's a shame her dismal fate was predestined, especially considering her replacement was (shudder) Dodo. She was a strong woman of action, sensitive, smart and handy with a ray gun. She had a great rapport with the Doctor and Steven, and her role as the action hero of the trio (sorry, Steven) didn't preclude a bit of fun - just listen to the three of them having a ball in the Christmas special episode The Feast of Steven, in which Sara's mistaken for an actress on a 1920's Hollywood film set. At the end of the episode, the trio celebrate the season by getting their drank on. Sara was anything but one-note.
Like Katarina before her, killing Sara off seems like a missed opportunity. It would have been a lot of fun to see how the character developed, particularly in the more-than-capable hands of Jean Marsh, a wonderful actress, arguably the most famous actor to play a companion in the classic series. She's perhaps best known in America for her role in the TV sitcom adaptation of the movie 9 to 5. Oh, and Upstairs, Downstairs. She won an Emmy and some Golden Globes for that, I think. But mostly 9 to 5.
I speak of Sara as a companion, but her official status has long been a source of debate amongst fans. She was never intended to last past this story, the BBC did not consider her the new "Doctor Who girl", and Jean Marsh herself insists to this day that Sara was not a proper companion. But for nine episodes she certainly felt like one - she traveled in the TARDIS, got caught up in more than one adventure (even if it was under one umbrella title), and, if not officially considered a companion by the Who office, was at the least intended to fill the role of girl companion for this story.
My position on the subject of whether Sara Kingdom counts as a companion is a firm "Who gives a shit?" Why not count her? It's not like there's such a thing as an "official" companion anyway, really - the new series has made that abundantly clear. Is Jackson Lake a companion? I guarantee in thirty years or so there will be officially licensed stories set between The Next Doctor and Planet of the Dead in which Jackson and Rosita finish their Christmas dinner with the Tenth Doctor and are whisked away by him for a whole string of adventures we just haven't heard about yet. So why not Sara? If it means more Doctor Who stories, I'm all for it.