Episode ... - "doctor Who" The Ambassadors Of Death:

is the third serial of the seventh season of Doctor Who , originally broadcast in seven weekly parts from March 21 to May 2, 1970 . It features Jon Pertwee as the Third Doctor in his first major venture into space during his Earth-bound era. Plot Summary

: A recovery mission, Recovery 7 , returns to Earth, but the occupants are kidnapped by criminals led by Reegan . It is discovered that the "astronauts" are actually radiation-dependent alien ambassadors who swapped places with the humans. "Doctor Who" The Ambassadors of Death: Episode ...

: Primarily credited to David Whitaker , though the final script was heavily rewritten by Malcolm Hulke , Trevor Ray , and Terrance Dicks . is the third serial of the seventh season

: The Doctor and UNIT eventually thwart Carrington's broadcast plans and arrange a peaceful exchange: the ambassadors return home, and the human astronauts are released safely to Earth. Production & Cast It is discovered that the "astronauts" are actually

: The kidnapping is orchestrated by General Carrington , a xenophobic ex-astronaut who intends to use the ambassadors to incite a war against their kind.

: Includes Jon Pertwee (The Doctor), Nicholas Courtney (Brigadier Lethbridge-Stewart), and Caroline John (Liz Shaw).

The story revolves around a mystery at regarding Mars Probe 7 , which has been out of contact for seven months.