One of the greatest mysteries of Doctor Who Season 7 is new companion Clara Oswald (Jenna Coleman), a brave and capable woman of today who somehow exists in different times and places. In “Asylum of the Daleks,” she is a resourceful space traveler named Oswin who, to her shock, discovers that she has been transformed into a Dalek. In the mid-season special “The Snowmen,” she returns as an 1892 barmaid who befriends the Doctor and helps him fight the Great Intelligence (Ian McKellen), with tragic results.
Because of this, the doctor calls Clara the impossible girl, and it turns out that the resemblance between the three versions of Clara is no coincidence. On Trenzalore, the returning Great Intelligence Agency (now played by Richard E. Grant) unveils his plan to invade the Doctor’s timestream and turn his life into a vast chain of losses. Clara figures out how to undo this by jumping into the creek herself, creating endless echoes of Clara’s helping the Doctor at various stages in his life. Her ability to affect the Doctor’s timestream in endless ways is similar to the Infinite Potential Leaf she uses to defeat Akhaten earlier in the season. In fact, the Doctor manages to save her with the same leaf.
Although Clara’s plan is successful, it is also quite tragic. The Doctor has already witnessed two versions of her horrific fate, and because she secretly fights the Great Intelligence’s interference in pretty much every single part of the Time Lord’s long timeline, it means that “Asylum of the Daleks” and “The Snowman” essentially are just two of their countless battles. Judging by the fates she suffers in these episodes, it’s chilling to imagine how often things end badly for her.