This entire story seems an exercise in decompressed storytelling. Don’t get me wrong, there is a good story buried in here, one in which humans have kidnapped a group of radioactive aliens. The humans are developing a way to exploit these deadly aliens, to use them for their own nefarious ends. The problem is, at the current pace, I’m not sure the story needed to be seven parts long.
Granted, I’m making this criticism in 2012. Television probably didn’t work that way in England in 1970. Most-likely, the producer set an episode count and ordered a story. It would then be up to the writer to meet the episode number. With the writing issues of this story, it probably isn’t a big surprise that the pace is occasionally glacial. Still, this story could be tightened to great effect.
At least it is different, though. This isn’t an alien invasion; it is a covert group using alien prisoners as weapons. This is a great idea to explore, especially as it has the potential to become somewhat personal for The Doctor. He is trapped against his will. He has fallen in with an international military organization. He could very easily become a weapon. Thankfully, The Brigadier offers him a certain degree of autonomy, but if he had fallen into different hands, The Doctor’s fate could have been quite different.
Three episodes to go.