The Doctor joins UNIT's investigation into the mystery surrounding Mars Probe 7. Space Control, headed by Professor Ralph Cornish, has had no contact with the astronauts on board since it started back from Mars seven months ago, and now the Recovery 7 rescue mission has run into similar difficulties.
This second ship does get back to Earth, but the astronauts are kidnapped after landing and Liz Shaw notices that the Geiger counter is at maximum. It transpires that the ship's occupants were not the human astronauts after all but a trio of radiation-dependent alien ambassadors who had swapped places with them.
The Doctor makes a solo flight in Recovery 7 and docks with Mars Probe 7, still orbiting in space. He is then intercepted by a huge alien spaceship and taken on board, where he finds the real astronauts unharmed. The aliens' Captain threatens to destroy the Earth unless their three ambassadors are released.
The Doctor is allowed to go and, after returning to Space Control, discovers that the kidnapping of the ambassadors is part of a scheme devised by xenophobic ex-astronaut General Carrington to discredit the aliens and convince the world's authorities to wage war against them. The Doctor and UNIT are able to thwart his plans and arrange the safe exchange of ambassadors for astronauts.
With the United Nations Intelligence Taskforce providing security, the British Space Programme under Professor Ralph Cornish oversees the launch of the Recovery Seven probe. This has been sent to Mars to make contact with the missing Mars Probe Seven and its three astronauts, who lost contact with Earth eight months earlier. The pilot of Recovery Seven, Charles Van Lyden, makes contact with the Probe but is then silenced by a piercing unearthly sound. The noise troubles the Doctor who travels with his assistant Liz Shaw to the Space Centre to investigate the situation, offering insights into the origin and meaning of the sound, which he interprets as coded messages. He also identifies a reply message sent from Earth and this is pinpointed to be coming from a warehouse seven miles away. Led by Brigadier Lethbridge-Stewart, UNIT troops attack the warehouse and engage in a gun battle with troops organised by General Carrington. Taltalian pulls a gun on Liz and the Doctor in the computer room.
Episode 2Taltalian escapes the room. Meanwhile Recovery Seven has returned to Earth and while UNIT is transporting it more of Carrington’s troops stage an ambush and steal the vessel. The Doctor relocates it, by which time the astronauts appear to be attempting to communicate. However, the Doctor discovers that the voices are merely repeating themselves, and will not answer his questions. The Doctor then orders the craft opened.
The craft is opened, and found to be empty, save for a recording of the astronaut's voices, and a high amount of radiation. Carrington has ensured the contents – three space suited astronauts – are detained elsewhere, feeding them radiation to keep them alive. Carrington is now introduced to the Doctor by Sir James Quinlan, the Minister for Technology, who explains that he is head of the newly formed Space Security Department, and that his actions were to protect the astronauts as they had been infected with contagious radiation. Quinlan states that they did not want the public to become panic-stricken and so Carrington had been acting with authority in his actions. By the time Carrington takes the Doctor and his friends to meet the astronauts the situation has changed again. A criminal named Reegan has organised their abduction, killing the soldiers and scientists protecting them. When the Doctor and Liz examine the situation they work out that human tissue could not have withstood the degree of radiation emitted to the astronauts, who are still in orbit, meaning the three space suits contain alien beings instead. In order to aid his own scientist, Lennox, a disgraced Cambridge professor, in maintaining the alien beings while they are incarcerated, Reegan lures Liz into the open, where his henchmen attempt to capture her. The chase leads to a pier, where Liz slips, and dangles helplessly
Liz is saved by the henchmen, and brought to Reegan, who forces her to help Lennox. Meanwhile, the Doctor learns that Taltalian was ordered by Carrington to sabotage the equipment, and receives a telephone call from Reegan warning him to stop interfering, holding Liz's life ransom.
Taltalian, in league with Reegan, quickly departs for the villains hideout, returning with a bomb that damages the equipment, and kills him. Together, Liz and Lennox build a device to communicate with and control the aliens, who are sent on a killer rampage at the Space Centre, killing Quinlan and others. As the Doctor checks Quinn's prone body, he is approached from behind by one of the aliens.
The Brigadier shoots at the alien, drawing it away from the Doctor, but is unable to stop it from killing one of his men and escaping. Liz helps Lennox escape, and the scientist goes to UNIT, wanting protective custody against Reegan's wrath. Despite the obstruction of the authorities, Ralph Cornish is determined to organise another space flight to Mars to investigate the situation. With Quinlan dead, the Doctor now decides to pilot the Recovery Seven probe ship himself, the ship's radiation levels having decreased considerably. Reegan, learning of Lennox's betrayal, plants a radioactive isotope in his cell, which quickly kills him. As the Doctor prepares to blast off, Reegan tries to sabotage the probe by increasing the feed of M3 variant. The Doctor survives the attempt on his life and succeeds in piloting the probe so that it connects with Mars Probe Seven. As Recovery Probe Seven docks with the Mars Probe, an unidentified object heads straight towards them, on a collision course.
The object is revealed to be an alien spaceship, which brings the Doctor aboard. Once there, the Doctor discovers the three original astronauts are unharmed but mentally deluded into believing they are in quarantine. An alien being now reveals itself to the Doctor and explains the humans are being held aboard the craft pending the safe return of the Alien Ambassadors. They had been sent to Earth following a Treaty between the race and mankind, but the terms of this agreement have now been broken because of the detention of the Ambassadors. The Doctor offers his personal guarantee to help return the Ambassadors to their mother ship and resolve the conflict before a state of war is declared, and is permitted to leave the alien craft and return to Earth. When the Doctor touches down he is gassed and kidnapped by Reegan, who takes him to Liz. Reegan’s real paymaster and the real organiser of the situation is revealed to them: General Carrington. Declaring that he had intended Reegan to kill the Doctor, the General pulls a gun on him, declaring that killing him is his "moral duty".
Reegan convinces Carrington to spare the Doctor, and make use of his scientific ability. The General reveals his actions have been prompted by xenophobia driven by his own encounter with the alien beings when he piloted Mars Probe Six some years earlier. His co-pilot, Jim Daniels, was killed on contact with the aliens and the General signed the treaty with the aliens to lure three of their number to Earth, where he hoped he could unveil their real agenda of alien invasion. The use of the ambassadors to kill people was similarly done to arouse public opinion against them. The next phase of his plan is to force the Ambassadors to confess their plot on public television. Leaving the Doctor and Liz working on a new and improved communication device to translate the aliens, Carrington departs for the Space Centre, where he aims to unmask the alien Ambassador before the eyes of the world – and then call on the powers of the Earth to blast the spaceship from the skies. Using his work on the translator as a cover, the Doctor transmits a morse code SOS to the Brigadier's men. UNIT soldiers then raid the secret base and rescue the Doctor and Liz, apprehending Reegan and his thugs. The Doctor races to the Space Centre and he and the Brigadier apprehend Carrington before he can make his broadcast. Carrington is taken away, protesting he was only following his moral duty. The Doctor arranges for Cornish and Liz to send the Ambassadors back to their own people, after which the three human astronauts will be returned.
- The Doctor - Jon Pertwee
- Liz Shaw - Caroline John
- Brigadier Lethbridge-Stewart - Nicholas Courtney
- Sergeant Benton - John Levene
- General Carrington - John Abineri
- Ralph Cornish - Ronald Allen
- Bruno Taltalian - Robert Cawdron
- Miss Rutherford - Cheryl Molineaux
- Collinson - Robert Robertson
- Grey - Ray Armstrong
- Sir James Quinlan - Dallas Cavell
- John Wakefield - Michael Wisher
- Reegan - William Dysart
- Lennox - Cyril Shaps
- Dobson - Juan Moreno
- Heldorf - Gordon Sterne
- Masters - John Lord
- Flynn - Tony Harwood
- Technician - Roy Scammell
- Control Room Assistants - Bernard Martin, Joanna Ross, Carl Conway
- UNIT Sergeant - Derek Ware
- Corporal Champion - James Haswell
- Private Parker - James Clayton
- Private Johnson - Geoffrey Beevers
- UNIT Soldier - Max Faulkner
- Alien Voices - Peter Halliday
- Alien Space Captain - Peter Noel Cook
- Charles Van Lyden / Alien Ambassador - Ric Felgate
- Joe Lefee / Alien Ambassador - Steve Peters
- Frank Michaels / Alien Ambassador - Neville Simons
- Walk-ons (uncredited) - Steve Smart, Rod Peers, Clive Rogers, Keith Simons, Tom Laird, Roger Minnis, Eric Kent, Stuart Myers, Ray Emmins, Vernon Preston, Les Shannon, Garth Watkins, Crawford Lyall, Doug Roe, Bruce Cox, B.G. Peath, Richard Pickford
- Assistant Floor Manager - Margot Hayhoe
- Costumes - Christine Rawlins
- Designer - David Myerscough-Jones
- Film Cameraman - A A Englander, Tony Leggo
- Film Editor - Don Goddard, Chris Wimble
- Incidental Music - Dudley Simpson
- Make-Up - Marion Richards, Teresa Wright
- Special Sounds - Brian Hodgson
- Studio Lighting - Ralph Walton, Geoff Shaw, Dave Sydenham
- Studio Sound - Gordon Mackie, Brian Hiles
- Title Music - Ron Grainer and the BBC Radiophonic Workshop, arranged by Delia Derbyshire
- Visual Effects - Peter Day, Ian Scoones
- Writer - David Whitaker, Trevor Ray (episode 1, uncredited), Malcolm Hulke (episodes 2-7, uncredited)
- Script Editor - Terrance Dicks
- Production Assistant - Nicholas John
- Director - Michael Ferguson
- Producer - Barry Letts
- At the start of the adventure, the Doctor has not yet forgiven the Brigadier for his destruction of the Silurian base. He can make solid objects vanish and a few minutes later, re-appear.
- This is the first story to feature Benton with the rank of Sergeant.
- The Doctor is fixing the TARDIS' Time Vector Generator, which sends Liz 15 seconds into the future.
- Liz can speak French.
- The aliens are not native Martians.
- The alien radioactivity is suggested as being conductible like electricity.
- Working titles for this story included The Invaders from Mars, Invaders from Mars and The Carriers of Death.
- An unusual title sequence was used for this serial, with the sequence cutting off after the show's logo, repeating the previous week's cliffhanger, then returning to the titles for the serial's name, writer and episode number.
- This was the last story written for Doctor Who by David Whitaker. He considered it his least favourite story, possibly because he ended up writing very little of it (see Writer credits above).
- The plot of this story resembles that of The Quatermass Experiment, where an astronaut who has apparently returned to Earth has in fact been replaced by an alien lifeform.
- Apart from Brigadier Lethbridge-Stewart, who retained his regular uniform, all UNIT ranks wore new futuristic-looking uniforms which only ever featured in this story. The usual velcro-fastened jacket, shirt and tie were replaced on this occasion with a zip-up jacket without lapels worn over a polo-neck sweater.
- Although the entire story was made on colour videotape, only the first episode is retained in this format; in fact, it is the earliest episode that survives in the series' original videotaped format, either in colour or B&W. (It is not, however, the first to exist in colour: See Spearhead from Space.) The remaining six episodes survive only as black and white film recordings and poor-quality domestic colour recordings made from a US transmission in the 1970s. This recording is severely affected by a rainbow-coloured pattern of interference that at times overtakes the entire picture.
- In 2002, a restoration project for the story's VHS release combined the usable colour information from the domestic recordings with the black and white picture from the film prints, creating a high-quality colour picture. In total, more than half of the serial's running time is presented in colour on the VHS release, including all of Episodes 1 and 5, and sections from 2, 3, 6 and 7. The remaining footage, including all of Episode 4, was not deemed suitable for colour restoration, and so remains in black and white. There have also been fan efforts to colourise the serial.
- Episode 1 - 7.1 million viewers
- Episode 2 - 7.6 million viewers
- Episode 3 - 8.0 million viewers
- Episode 4 - 9.3 million viewers
- Episode 5 - 7.1 million viewers
- Episode 6 - 6.9 million viewers
- Episode 7 - 5.4 million viewers
to be added
- The exterior isotope factory scenes were filmed at Little Marlow Sewage Treatment Works.
- Southall Gas Works in Middlesex and Blue Circle Cement Works in Buckinghamshire were used for the Space Headquarters.
- Roads in Marlow and at the Marlow Weir were used for the chase sequences with Liz Shaw. Wycombe Air Park was used as Heldorf's lab, and Beacon Hill for Reegan's hideout.
- Aldershot, Hampshire, warehouses on White Street, TCC Condensers in Ealing, and Folley's Gravel Pit at Spade Oak were also used.
- All interior scenes were filmed at BBC Television Centre Studio 3.
- In Episode One, when the video screen retracts, the CSO image stays for several seconds.
- When the spacecraft rotates, the image from the cockpit camera rotates with it (it should be fixed on one point).
- From this story onwards no military personnel ever moves between 'attention' and 'at ease' properly.
- 'Variant' is spelt 'varient' on location props.
- Taltalian's accent is French in the studio and British on location.
- Recovery Seven's nose cone changes colour between prop and model shots.
- Quinlan's office safe slips about as the alien tries to open the door.
- The screen that the Doctor and Brigadier use to triangulate the signal wobbles when it is touched.
- When the capsule is landing, it is moving across the map of the Atlantic far faster than the announcements indicate.
- The Doctor is still nursing a grudge against the Brigadier for blowing up the Silurian hibernation chambers in DW: Doctor Who and the Silurians.
- The Mars Probe space program appeared in two novels.MA: Who Killed Kennedy revealed that the shuttles were developed from technology taken from International Electromatics.
- In NA: The Dying Days it was revealed that the program was abandoned when Mars Probe 13 accidentally encountered the Ice Warriors and it was agreed that Earth would stay away from their territory.
- DW: The Christmas Invasion also involves aliens attacking Earth after they intercept a probe sent to Mars.
- BFA: Red Dawn also features a manned mission to Mars.
- John Benton makes his first appearance since DW: The Invasion.
- This story occurs after: TVC: Doctor Who and the Rocks from Venus
- This story occurs before: DWA: The Mind Extractors
Home video and audio releases
Editing for VHS release completed by Doctor Who Restoration Team.
Novelisation and its audiobook
- Main article: The Ambassadors of Death (novelisation)
- Novelised as The Ambassadors of Death by Terrance Dicks it was published by Target Books in May 1987 and was the final Third Doctor serial to be adapted. The Third Doctor's era was, as a result, the first to be completely adapted by Target Books.
- The Ambassadors of Death at the BBC's official site
- The Ambassadors of Death at Shannon Sullivan's A Brief History of Time (Travel)
- The Ambassadors of Death at The Locations Guide