Terror Of The Autons is the first serial of the 8th season. It's still the 3rd Doctor played by Jon Pertwee. The 4 episodes first aired January 2 1971 and ran through the 23rd of the month. There's a new companion called Jo Grant who is played by Katy Manning. She's not a scientist and the Doc is cranky about that but he can't fire her himself so he lets her stay. Nicholas Courtney returns as Brigadier Lethbridge-Stewart and Roger Delgado makes his first appearance as The Master.
The Master arrives on earth in a Tardis disguised as a horsebox. He takes over a circus and steals the Nestene unit left over from an earlier story. He uses a radio telescope to beam out a message to the nestines. The Doctor hears about the thief and the trouble at the radio telescope and suspects something. He wasn't expecting to see the Time Lord that comes to warm him that The Master is on earth. The Master takes over a plastic factory. He starts building Autons and kills some people who don't want to give up their factory. The Doctor chases around sparing with the Master form show to show. Sometimes one or another of the cast gets captured and escapes. Between there's some fightin' by the UNIT team and some science yakkin' from the Doc's lips. The violence got some bad press at the time the show was aired. The Doctor does eventually thwart The Master's plan but the evil one escapes. He'll have to stay on earth for a while, the Doctor stole a part from his Tardis, and according to the featurette on character he will return. It was a pretty good story that moved along better than most of the longer serials.
There's another featurette on the disc and a commentary that I didn't finish but might before the disc goes back to the library. The featurettes were interesting enough. I like that they fill you in on a lot of detail about the show's creation. Terrance Dicks is the script editor and Barry Letts is the producer. They ahve some good comments on their contribution to the series.