Review for all 4 parts:
This pseudo-historical story has the TARDIS arriving at the site of Heathrow airport to return Tegan but finding they are in the 1660s during the plague and that some lizard-like aliens the Terileptils have crash landed there and are up to no good.
This was the first contribution of Eric Saward to the show. He wrote the story and was soon made script editor taking over for the production of stories including a couple which were broadcast before this one. Saward does well as a writer although he would turn out to be not consistently good in my opinion as a script editor.
Saward's story is very interesting and fun. The first couple of episodes are quite slow but set the scene really well with some excellent period settings and enjoyable scenes. The introduction of the Terileptils is a decent new alien who have menace and intelligence in their concept. The alien costumes are not perfect but the faces are good I think and they present a suitable threat. The dialogue is very good and intelligent, one of the main strengths of this serial.
Michael Melia puts in an excellent performance as the lead alien, delivering his lines really well. Michael Robbins is also brilliant as Richard Mace, a rich character who enriches the story and has quite a journey across the 4 episodes. Other guest roles are very good and the TARDIS crew are solid. The relationships are strong and apart from an annoying scene at the start with Tegan getting angry they do their jobs well.
Peter Davison is excellent as The Doctor. He shows some depth and toughness here as well as his compassion and decency. He is on top form. We also see the demise of the sonic screwdriver which had been a very oft used device but would not be seen again until the 1996 movie with the 8th Doctor.
I really liked this story a lot, especially the 3rd and 4th episodes when the action, the plot and the dialogue kick into top gear. I think it is great. The linking in of historical events is nicely done, there are nice period locations and a fun story.
My ratings: Parts 1 & 2 - 9/10, Parts 3 & 4 - 10/10. Overall - 9.5/10.