Blobs are appearing. Horrifying, grotesque, unconvincing, blobs! But they’re disappearing people nonetheless so the Doctor is sent to have a poke around. Turns out the blobs have come from a parallel universe that is sucking all the energy out of our universe. The unconvincing blobs are getting larger and The Doctor doesn’t know what to do. Sadly for him, neither do the Time Lords. But they decide to break their own laws and, to use a Ghostbusters analogy, "cross the streams".
And lo, The Doctor’s second and third incarnations meet. And it’s bloody great.
The chemistry between Troughton and Pertwee is instant. They bicker, they squabble and they work together superbly. They remind us how different the Doctor’s incarnations can be but that he’s always the same man, just going about the same things with a different approach.
The story is, to me, very ambitious. It gives us a history to the Time Lords, almost an origin story. We meet Omega, one of the founders of Time Lord society, and paints him as a misunderstood but pretty insane, genius.
It is one of the greatest pities in the history of the show that Hartnell could not appear fully due to illness but his limited contributions are enjoyable nonetheless as the first Doctor patronises and tries to organize his latter selves.
As the story progresses the two main Doctors use their own characteristics in tandem. Troughton acts the buffoon but gets Omega’s goat up exactly as he wants, Pertwee is stern and plotting.
The twist (Omega’s fate) is awesome and his character is well developed. We’re basically shown a bitter genius who created a new society but couldn’t be a part of it and has seen his own fate in contrast to the greatness achieved by the society he forged, along with his ultimate downfall.
Not only this, some of the imagery created is fantastic. Omega’s mask gave me nightmares for years and the process of his unveiling is superb.
This story set the precedent that has lasted ever since. We may have only seen Doctors meet each other on a few occasions but they are always memorable. This story was written for the show’s 10th anniversary and poor old Steven Moffatt pretty much had no choice but to write some sort of Doctor crossover for the 50th.
And of course, the script is great. Benton entering the TARDIS for the first time and, of course, pretty much anything that comes out of the Brigadier's mouth...
It’s possible that this is because I remember this from my youth but I love this story. There is some scientific nonsense but the development of the Time Lords, the development of the Doctor and the creation of Omega make this an incredibly memorable and effective story for me.
9/10.