The Doctor is a Time Lord. Whereas most of us face death when our bodies wear out, a Time Lord is able to regenerate. The TV Series and TV Movie featured ten incarnations. The Doctor featured in "Devious - Halfway to Oblivion" has been extracted against his will from his time-stream midway though the regeneration between his second and third 'selves' - the Doctor IS the Halfway.
This Interim Doctor finds himself in unfamilar surroundings with a jumble of memories. His past seems newly-created. Stumbling to make sense of these strange memories, he is drawn ever closer to "The Test". One he must complete in a certain way - or face Oblivion.
Many people are watching The Test as it unfolds. Reputations depend on the results.
The Test has many players.
Not all play by the rules.
With the daleks as hidden players, no-one is sure who to trust. With a fearsome time-weapon of mass-destruction nearing completion, only one person holds the key. With ever-increasing time disturbances throughout the story the Doctor realises the events at the outset are being caused by the events at the finale, and only he is able to make sense of this maze. Seeing the sacrifices others have made for their cause, he starts to realise his own fate.
However during the tale he realises he is an Interim. He is also offered the chance to be real - to be the next true incarnation of the Doctor rather than just a temporary one. Is that an allegory? - we are recognising on our own script that we are not real Doctor Who - the Doctor is told he is not real, but he is offered the chance to be.