I gotta hand it to Big Finish. As brilliant as The Dalek Invasion of Earth is, they somehow found a way to squeeze in another chapter without taking anything away from the first or cheapening the quality of the second. Or is it the third? Renaissance of the Daleks also featured an entry into the famous invasion, but Masters of Earth just comes out looking better.
As brilliant as The Dalek Invasion of Earth is, I'm still not that big a fan of 1) Daleks and 2) the serial. So if I say this story works and has you wanting more, then it means something. This time, the Sixth Doctor and Peri arrive ten years before his first incarnation is scheduled to defeat the Daleks and in a rare moment of temporal caution, the Doctor wants out. He understands the danger. Like The Waters of Mars, this is one adventure he cannot have as it will severely screw up the timeline. And yet in traditional Doctor Who fashion, the Doc and his companion are eventually pulled into this particular prequel adventure and forced to have it.
A bold move from Big Finish as stories like these that rely so heavily on continuity to work can easily be screwed up by saying or doing something that would contradict what's already been established. They know fans will notice even the tiniest deviation and will lash out. Thankfully, this story avoids those mistakes and gives us a peculiar mix of a stand alone prequel and a continuity heavy plot which relies on the Remember The New Guy trope. It works. It doesn't feel forced and while listening to it, one can hear the parallels between Masters of Earth and The Waters of Mars. It's intense, it's full of suspense and leaves you wondering what bad something is going to happen next. Really, you can't help but wonder every step of the way if something anti-continuity is about to doom the Doctor.
There are a few solid twists during this story, but also a few predictable ones. Other elements that are love/hate are the Robomen. Seriously, the Robomen suck. Thank god for duplicates and nano-converted people because again...Robomen suck!
Something I feel could've been explored more is the post-reunion between the Doctor and Peri. It is brought up, but still feels sort of brushed under the carpet. Peri is still the same Peri, harbors no ill-will towards the Doctor and feels content to continue traveling with him despite what happened to him. True, I don't want the story to be overshadowed by this talk like with 12/Clara, but a little bit extra couldn't have hurt.
Rating this story: 7.5/10. A good new chapter added to the Dalek Invasion of Earth.