A 'Doctor Who' Fan-Favorite Character Could Make One Final Appearance This Christmas

Note: This article contains spoilers for Doctor Who's Episode 6 of Season 10, "Extremis."Doctor Who has given us many twists and surprises in the current series of the hit BBC show, and astute fans haven't missed the same reference that keeps popping up almost every week. In Episode 6 of Season 10, titled "Extremis," one character in particular played a vital part of the story: The one, the only River Song, played by Alex Kingston.

Kingston's last appearance in Doctor Who was in the 2015 Christmas special, "The Husbands of River Song," in which viewers saw River and the Doctor share their final moments together before she headed off to the Library for one last adventure. River Song played an important role in the latest episode "Extremis," by preventing the Doctor, played by Peter Capaldi, from executing Missy, his closest frenemy.

But how could River play an important role if she wasn't even on screen? Nardole attended the execution site and read a passage from River Song's diary, which then got the Doctor to ruminate on what he was about to do. The passage from River Song's diary read:

"Goodness is not goodness that seeks advantage. Good is good in the final hour, in the deepest pit, without hope, without witness, without reward. Virtue is only virtue in extremis. This is what *he* believes, and this is the reason above all I love him, my husband. My madman in a box. My Doctor.”

Hardcore fans may have also noticed that "Extremis" answered one question in particular: How did Nardole return to Doctor Who?

Nardole was sent by River Song and confirmed as much by admitting it when questioned by the Doctor: "I followed you from Darillium on the explicit orders of your late wife River Song." This of course refers to their final moments together before the Doctor witnessed River's death.

When reading the passage, fans noticed that Nardole was reading from River Song's personal diary, before being questioned on where he got it from. It is presumed that either River personally gave it to Nardole, or Nardole rescued it from the Library, which is where the 10th Doctor left it at the end of "Forest of the Dead," the ninth episode of Season 4.

Can We Expect River's Christmas Return?

Doctor Who showrunner Steven Moffat has been leaving subtle hints about the return of River Song. This started off in season opener "The Pilot," when fans spotted a photograph of River and the Doctor's granddaughter Susan on the desk in his university office.

The second hint toward her potential return was in Episode 2, titled "Smile." Some fans may not have seen this as a hint, but others have studied River and the Doctor's timeline and picked up on the Doctor's quote, "I'm not that fond of fish, except socially." Despite it having been an off-screen event, fans know this is referring to the Doctor and River having a karaoke night with a chap named Jim the Fish.

The hints continued in Episode 3, "Thin Ice," when fans noticed this reference straight away. "Thin Ice" is set during the last Thames frost fair in 1814, and the Doctor mentioned to Bill (Pearl Mackie) that he had been there a few times. If you cast your minds back to the tense and revealing Season 6 episode "A Good Man Goes To War" from 2011, River is seen retuning to prison, when she bumps into Rory. On seeing him, River said,

“It’s my birthday — the Doctor took me ice-skating on the River Thames in 1814. ... He got Stevie Wonder to sing for me under London Bridge.”

With the latest River Song reference in "Extremis," it probably isn't long until another hint drops. But how does all this tie to the character's return? Fans know current Time Lord Peter Capaldi is departing Doctor Who during this coming Christmas special and it is currently unknown if his latest companion Bill will be beside him when he regenerates.

So has the out-going Moffat planned for Kingston to make one final appearance in Doctor Who and say goodbye to her husband as he regenerates in front of her? This seems like the perfect love-story send-off for Capaldi, especially now that it's been revealed his last episode will be a tale of hope and redemption.

With River's return remaining a mystery, it's also been hinted that one beloved character will make a return to Doctor Who alongside a not-so beloved character, this being the First Doctor, who will be portrayed by David Bradley, and Clara "Oswin" Oswald, respectively. All eyes are currently focused on the BBC as we await the news confirming the guest list for the Christmas special, and of course who will be replacing Capaldi.