Doctor Who: The Ambassadors of Death (Part 4)

"The Ambassadors of Death (Part 4)" is the fifteenth episode of series seven of the British science fiction television series Doctor Who and the 257th episode of the series overall. It is the fourth chapter of the "Spearhead from Space" serial and was directed by Derek Martinus and written by Robert Holmes. It first aired on BBC One on April 11th, 1970.