Just finished this wonderful serial; another classic 3/Delgado format with "Master forms an alliance with an alien who turns on him and then he needs the Doctor's help to defeat the alien and then the Master escapes at the last possible second". And, if you're wondering why I used the slash between "3" and "Delgado", I think the Guide's screenshot says it all (:

The pacing felt appropriate, the plot was intriguing, and the character development throughout the serial was wonderful (thinking especially of how the Brigadier began smiling a lot in the last couple episodes, admitting to himself that he's happy to be keeping the Doctor around, and allowing himself to feel relief and joy that his men are alive). 3 and the Brig were acting like such an old married couple in those last few minutes! Love to see it!

I thought the Master killing Barnham felt sudden and cruel. I didn't expect Barnham to survive this, but this felt out of nowhere, and totally out of line with the Master's usual behaviour. I was also quite unhappy with the lack of willingness to engage with the ethics of the Keller machine as it was (removing the autonomy of prisoners, and any chance at an actual, honest rehabilitation), not just as it could be used. I also felt that the writers didn't even try to adhere to science in any way whatsoever - it was funny at first, with the idea that the nerve gas missile could be safely disposed of by tossing it in the ocean, but it really started to get on my nerves with the Keller machine "removing evil impulses". It would have been so, so easy to just say that it "identified areas of the brain associated with violent thoughts/actions and damaged them using electricity, but really it was the alien feeding on brain waves that damaged the brain", something like that.

That said, the Brig being able to show more emotion than just annoyance made me enjoy this immensely, so overall, giving this one a 4.5/5.