Katerina, Bret Vyon and Sara Kingdom are dead, a revolving door has been installed in the production office, there are Daleks all over the place and things are getting a little bit racist in here. And Billy's upset (but not about the racism, obviously). It can only be Doctor Who's third season.
In this episode of Doctor Who in Ten Seconds, Brendan deftly summarises Galaxy 4, Mission to the Unknown, The Myth Makers, The Daleks' Master Plan, The Massacre, The Ark, The Celestial Toymaker, The Gunfighters, The Savages and The War Machines.
As always, a vastly more lengthy treatment of the same stories can be found in these episodes of the Flight Through Entirety podcast.