Ever since she teamed up with the Sixth Doctor at the end of `The Girl Who Never Was', we've all been asking the same question - just how will the writers resolve the apparent paradox of the Eighth Doctor not remembering Charlie when he first meets her on the R101? It was obvious that a complicated adventure full of some interesting concepts and hard core sci fi would be required to resolve the issue. If not handled well then it could be just a confusing mess, so it was with some trepidation that I started to listen to this, knowing it would be Charlie's farewell.
Forgetting the Charlie problem for a moment, this is an excellent story in its own right. The Doctor and Charlie are forced to land on a post apocalyptic Earth, where the inhabitants are in the grip of some strange madness. A select few are in receipt of medicine from the mysterious Viyrans, with the condition that they make photographic records of all the untreated humans. But just what do the Viryans really intend? And what was the source of the infection?
A really great tale that plays with your preconceptions, and interesting in that it shows certain decisions from the Viryans viewpoint, a cold, logical, alien viewpoint that looks at the big picture and does not feel sympathy, or indeed, any other emotion. Added to this is the resolution to the Mila situation and the Charlotte Pollard problem. Both are done in a satisfying manner that ties up all the loose ends.
Colin Baker shines as Six, full of compassion and energy. India Fisher is excellent as Charlie, in the final scenes I was really moved by her performance. A decent script and well directed. What more do you need?
I would recommend listening to `Storm Warning' and a few of the Eighth Dr/Charlie adventures, as well as `Patient Zero' and `Mission of the Viyrans' before listening to this, as this is the end of a long running story arc and there are lots of continuity references.