Spearhead from Space marked the debut of Jon Pertwee, the third actor to fill the title role of Doctor Who, and was also the first series episode shot in color and on location. Recovering from his second regeneration, the Doctor crash-lands in the British countryside amid an odd meteor shower. He is taken to the hospital by members of a special branch of the U.K. military known as UNIT (United Nations Intelligence Task Force (leaving off the "F" for savings, one assumes), where two more series debuts take place as Brigadier Lethbridge-Stewart (Nicholas Courtney) and scientist Liz Shaw (Caroline John) arrive on the scene, heading up an investigation into the strange falling rocks. Graced with just a bit more panache than his predecessors, the new Doctor also has a bit more razzle-dazzle at his disposal, as the series begins a trend toward flashier gadgets and showier vehicles. In addition to several Doctor Who TV spots, a rarely seen UNIT recruiting film is featured on the DVD.
This is item 1 in The Doctor Who: The Third Doctor, Jon Pertwee (1970-1974) Series.