The TARDIS reforms itself after what appears to be a cataclysmic explosion in space, only to become the target of a missile fired from the dark side of Earth’s moon…in 1968, when there still isn’t a human presence there. The timeship finally materializes in a nondescript field on Earth, but instead of a police box, it’s completely invisible. The Doctor, Zoe and Jamie set off for London on foot to seek Professor Travers’ help with the TARDIS’ visual stabilizer circuit, but soon hitch a ride on a passing truck, whose worried driver informs them that they’re in danger as long as they’re on International Electromatics property. He gets them safely out of IE’s corporate compound, but is then gunned down in cold blood by armed IE guards.
In London, the Doctor and friends discover that Professor Travers has gone to America with his Yeti findings, but his friend Professor Watkins might be able to help. But Watkins has gone missing – he’s never returned from International Electromatics – and his niece is holding down the Fort. The Doctor and Jamie return to IE’s headquarters building, where they cause just enough trouble to get a personal audience with the head of the company, Tobias Vaughn. The Doctor immediately suspects that Vaughn is up to no good, but he and Jamie don’t have time to think about it before they’re intercepted by two cars that have been following their movements. They’re taken to the mobile headquarters of a military organization called UNIT – the United Nations Intelligence Taskforce – whose British branch is headed up by their old friend Lethbridge-Stewart, now promoted to Brigadier. The Brigadier and his troops are monitoring IE closely: many brilliant, prominent scientific minds have entered, but none have left. The Doctor suspects that Tobias Vaughn wants control of more than just the world’s largest maker of electronic devices…but whose help does Vaughn have to pull off such a coup?
written by Derrick Sherwin
from a story by Kit Pedler
directed by Douglas Camfield
music by Don Harper
Guest Cast: Nicholas Courtney (Brigadier Lethbridge-Stewart), John Levene (Corporal Benton), Murray Evans (Lorry Driver), Walter Randall (Patrolman), Sally Faulkner (Isobel Watkins), Geoffrey Chesire (Tracy), Kevin Stoney (Tobias Vaughn), Peter Halliday (Packer), Edward Burnham (Professor Watkins), Ian Fairburn (Gregory), James Thornhill (Sergeant Walters), Robert Sidaway (Captain Turner), Sheila Dunn (Operator), Edward Dentith (Rutlidge), Peter Thompson (Workman), Dominic Allan (Policeman), Stacy Davies (Perkins), Clifford Earl (Branswell), Norman Hartley (Peters), Pat Gorman, Ralph Carrigan, Charles Finch, Richard King, John Spradbury, Peter Thornton (Cybermen), Peter Halliday (Cyber Director voice)
Notes: Parts one and four of this eight-part story (the only story of that length in the show’s history) were lost in a purge of black & white BBC shows after the BBC switched to color. (Ironically, part one of 1974’s Invasion Of The Dinosaurs, a Jon Pertwee story, was simply titled Invasion to avoid giving away that story’s adversaries, and it was mistaken for part of this story and junked, rendering an otherwise intact color story incomplete. A B&W copy of part one of that story was recovered later.) In 1993, BBC Video released The Invasion in incomplete form with Nicholas Courtney narrating encapsulated versions of the missing episodes, while a 2006 DVD release took the unprecedented step of completely reconstructing the missing segments with cartoon-style animation.
Broadcast from November 2 through December 21, 1968
LogBook entry & review by Earl Green
written by Kit Pedler & Gerry Davis
(Swann), Adam Verney (Colin), Margaret Hickey (Mary), Dibbs Mather, Bob Anderson, William McGuirk (Guards)
Colin Warman (Yeti), Jeremy King (Yeti), Roger Jacombs (Yeti), Derek Pollitt (Evans) 
