By now, you already know that Alex Kingston's River Song is returning for the "Doctor Who" season 9 Christmas Special. Plot details haven't been revealed, but one theory suggests that the episode could be the springboard to a larger story arc.
"I would hazard a guess that the reason for River's return could be linked with the Doctor's search for Gallifrey," Doctor Who TV's Mark McCullough speculated.
"The search is likely to pick up pace by the time Christmas comes around, so it is entirely plausible that would mean that River could be involved."
Before reaching the conclusion, McCullough said that fans will soon be seeing a version of River from before her appearance in the library in season 4.
As fans may recall, River Song died in "Forest of the Dead" saving the Tenth Doctor (David Tennant) and Donna Noble (Catherine Tate). The Doctor then saved her consciousness on the library's computer system. River's TARDIS-shaped journal containing accounts of all her run-ins with the Doctor is left in the library.
Her last appearance on the show was on the episode "The Name of the Doctor," where she appeared as an image in Clara's, and later the Doctor's, consciousness.
During the sidelines of Comic-Con 2015 last July, Peter Capaldi said it was the Doctor's "duty" to find his home planet, as Franchise Herald reported. However, speculations persist as to Gallifrey's manifestation in "Doctor Who" season 9.
As DWTV said, River could have known the planet's fate before going to the library. Then again, this would run against her actions in "Name" and would lead to a destiny paradox.
The same could be said of Missy (Michelle Gomez), assuming she is a post-Simm incarnation. She would have had to escape the Time Lord homeworld to make sure Clara and the Doctor stick together.
"There is a lot of Timey-Wimey there which would be fitting of Moffat's preferred writing style," McCullough said.
Perhaps River Song's journal may hold the clue to what happens next, DWTV speculated.
The "Doctor Who" Christmas Special will air on Christmas Day. Season 9 premieres on Sept. 19.
