*minor spoilers*

Mike's betrayal really does hit pretty hard when you've been following this era, but the story does a good job of keeping him sympathetic

Anyway if you've ever heard of this serial having some of the worst, most distracting SFX in the entire show... well that's all true. But once you get past that there is a really cracking, tense story. Really feels like a throwback to Pertwee's first season in many ways