There was no mystery about what the arc for 2009 meant. The Doctor was about to die, an event that would be heralded by four knocks. This becomes more of a character arc han a plot arc. What does the Doctor do when he knows his incarnation is reaching its end.
This very arc had been played out in other media, twice in the Doctor Who books alone. The writers of both the 7th and 8th Doctors, decades apart, were aware that a new Doctor had taken over and that the current incarnation must take their bow.
In the Virgin books the 7th Doctor, the perpetual planner and schemer, was made aware that he was ‘8th man bound’ something that terrified him. It was suggested that he’d played a dangerous Gallifreyian game to glimpse his future incarnations but he’d not seen beyond is 7th incarnation.
He’d not been able to plan further than that and there was still so much that he had to do. The final books portrayed the Doctor becoming worn down, his companions leaving him and finally alienating the one companion who had stayed with him.
In the final 7th Doctor book, ‘Lungbarrow’, the Doctor returned to his ancestral home to face demons from his past. It proves to be a cathartic experience and even as accepts a mission from President Romana he remembers that there is still a future for him, after all he hasn’t been Merlin yet (as seen in ‘Battlefield’).
The 8th Doctor was less perturbed by his approaching demise. He was granted glimpses of (multiple) 9th Doctor’s, most noticeably in ‘The Tomorrow Windows’, but was more concerned for his friends than himself.
‘The Gallifrey Chronicles’, the last 8th Doctor BBC book, left his fate open ended. The Doctor stands at the edge of shaft, dangerous monsters far below. Even if he defeats them there are more monsters he must face throughout space and time and one day he’ll fall.
Taking his companion’s hands the Doctor leaps.
Even in the main series the demise of the Doctor’s companions was foreshadowed twice. In ‘The Satan Pit’ the Beast claims that Rose will fall in battle. This comes to pass in ‘Doomsday’ when Rose is trapped in another dimension, mistakenly recorded as the people who died during the alien attack on Canary Wharf.
Donna also learns that her future might not be so rosy when River Song, a companion from the Doctor’s future, recognises her name and says she is sorry. Later mad Dalek Caan, having been exposed to the time vortex, foresaw that the Doctor’s most faithful companion would die.
Ultimately Donna didn’t die, just that her memory of the Doctor and thus her time with him would be erased. The person she was would vanish as if it never existed. A grim fate to be sure but she was still alive.
The Doctor’s own knowledge about his fate his delivered in an equally mystical manner. A psychic bus passenger in ‘The Planet of the Dead’ warns him that his song is ending and that “It is returning. It is returning through the dark and then Doctor…oh but then….he will knock four times.”
For the first time even the spin off shows were being used to push the story arc. In the Sarah Jane Adventures ‘The Wedding of Sarah Jane Smith’ the Doctor encounters the Trickster who is aware of the Doctor’s future, making mention that ‘The Gate’ was waiting for him.
In ‘Waters of Mars’ the Doctor is trying to change history, preventing the deaths of people even if it is supposed to happen. Certainly this could be seen as his own attempt to see if he can prevent his own fate.
When he realises he gone to far he receives a visit (or vision) of an Ood, the same race who also announced that his song would be ending soon. This is the last straw for the Doctor. His own actions have confirmed that he is at the end.
Before he follows up this vision by visiting the Ood in ‘The End of Time’ he has a last stab at delaying the inevitable, having a series of unseen bawdy adventures. Much of the first part of the final 10th Doctor adventure is taken up with his reluctance to die.
The story arc is a strange one to review as we all knew what the ending would be. We might not know the circumstances but we knew the Doctor was going to die. It is interesting that the Doctor himself was also aware of this.
Viewed on these terms the story arc helped to spark some interesting moments, if not stories, for the final year of the 10th Doctor. Even before the prophecy in ‘The Planet of the Dead’ the Christmas special ‘The Next Doctor’ played with the notion that the Doctor was meeting a future incarnation. Although he quickly learnt that wasn’t the case he had to acknowledge that his current form would only last so long.
Once again the idea works better than the implementation. There is little reason for this prophecy to exist within the Doctor Who universe. The ‘Four Knocks’ is unconnected to the villains main plan and its meaning is only that it happens when he is about to die.
In a similar way to Donna being the focal point of events leading to her becoming Donna-Doctor it is suggested that the universe has been pushing Wilf into the Doctor’s path because his fate was unavoidable.
Certainly there is a lot of potential in a character gaining future knowledge of their death. In a time travelling story there are much better avenues to gain this information than psychic visions. Who knows what someone might learn when they travel into their own immediate future.
The current season of Doctor Who is exploring this idea right now, with the Doctor’s companions witnessing his (apparently final) death. There are big ideas here, characters wrestling with their own mortality.
It is a great example of a thematic or character arc rather than a plot arc. Themes and ideas can be spread across several adventures to create a specific mood. The pay off is the final adventure, where that theme becomes part of the plot.