After losing contact with the Mars 7 probe for seven months since leaving MARS another astronaut - Charles Van Lyden - is sent by Space Control into space in a rescue capsule to investigate what happened. In Space Control UNIT are also called in to help with investigations. When the rescue capsule reaches Mars Probe 7 Charles confirms that it is the correct craft and starts the link up procedure.
Back at UNIT the Doctor is still trying to get his TARDIS working. Whilst reactivating the Time Vector Generator Liz is sent a few seconds into the future, and the Doctor is also sent a few seconds into the future. After they have both returned to the same time the Doctor sees the Brigadier at Space Control on a television, and watches the link up with Mars Probe 7.
As Charles opens the hatch to Mars Probe 7 there is a high pitched sound which is relayed to Earth via a live video feed. Watching at UNIT the Doctor realises he has heard the sound before, but cannot remember when. Sensing trouble the Doctor and Liz head off for Space Control.
Mars Probe 7 and Recovery 7 are in orbit around Earth, but all radio contact has been lost. When the Doctor arrives he tells them the sound they heard was a message, and shortly afterwards a second message is sent and everyone in Space Control hears a second high pitched sound. When there is a third sound the Doctor tells them the message was different - the third one was a reply - from somewhere on Earth.
UNIT arranges for different nations to monitor the signal, and when they hear it again France is able to pinpoint the origin - London. Meanwhile Professor Cornish, in charge of the Mars mission, is preparing Recovery 8 to up to investigate what has happened to Recovery 7.
UNIT personnel perform a local triangulation and determine the message is being sent from a warehouse only seven miles away. A squad of UNIT soldiers, along with the Brigadier, storm the warehouse. They are met by resistance from several armed men. As the two sides start fighting the two men who had been sending the signals set a self destruct mechanism before escaping.
At Space Control attempts are still being made to contact the stricken craft. Athens reports that a solar flare is expected within the next twenty-four hours. On board Recovery 7 the message is being received, but the craft is empty.
The Doctor has been trying to decode the messages, but to do so he needs more computer time. Doctor Taltalian is in charge of the computer, but is being obstructive. The Doctor tells Cornish, who orders Taltalian to be co-operative. When the Doctor returns to the computer room he and Liz are met by an armed Taltalian, who takes the tape containing the message from the Doctor. The Doctor holds out the tape, but it disappears. Moments later the Brigadier enters, and Taltalian runs off. Moments later the tape re-emerges in the Doctor's hand.
The Brigadier tells the Doctor that they managed to capture some men from the warehouse, and that one in particular seems to know something. When the Doctor talks to him he realises they are not going to get any information from him, but also that he is a soldier, and that he is acting under orders - one of which was not to harm the Brigadier. During the interrogation they have a message from Cornish that the capsules have separated, and that Recovery 7 is returning to Earth.
Recovery 7 starts to enter the atmosphere, but they are still unable to contact the crew, but are able to control the craft's descent, although they can no longer control the landing site, and the craft is due to land somewhere in the south of England. The Doctor, Brigadier and Cornish track and find the capsule, but the occupants do not open the hatch. The Brigadier asks for a route to be cleared as they fetch the capsule back. The Brigadier is unaware that his communication has been eavesdropped, and someone else also knows the route.
The lorry carrying the capsule is given a UNIT escort, but the convoy is attacked by a helicopter, and the occupants start dropping explosives. Two of the occupants seize control of the lorry and drive away with the capsule. The Doctor, who had been having car troubles, follows the convoy at a distance, and is surprised when he sees the lorry coming towards him. He pulls across the road in front of the lorry, and tells the men who have taken it he needs their help to push Bessie out of the way. After they do so he activates an anti-theft device, and the two men's hands are stuck to the car as the Doctor drives off with the lorry.
At Space Control the Brigadier is explaining what happened to Cornish when he sees the capsule, and the Doctor. Whilst they have been away Liz has been working on the messages, and realises they are from an alien intelligence. The Doctor, Liz and the Brigadier report what they have found to Sir James Quinlan, but he doesn't do anything to help. Meanwhile Taltalian's assistant, Dobson, reports to his superiors that the Doctor and Liz have started to break the code.
In the capsule room Cornish hears a message from the crew, but when it repeats the Doctor suggests that they cut open the capsule, and they find it empty. The Doctor suggests that the crew may have been taken from the capsule at some point, but the Brigadier says the capsule has been watched the whole time. Cornish tells them there was a short period of time when UNIT ordered a security check - a check that the Brigadier had not authorised. Liz, having looked at the capsule, makes a startling discover. The Geiger counter is at maximum. There had been some much radiation in there that if it had contained people they would be dead.
In another facility the occupants of the capsule are being treated by scientists, and under the supervision of General Carrington. The scientist is trying to reduce the radiation, but Carrington orders him to increase the radiation.
The Doctor, Liz and the Brigadier report the capsule problem to Quinlan. Whoever order the security check had proper authorisation, and if it didn't come from the Brigadier it had to come from higher up. The Doctor demands answers from Quinlan, and he introduces them to General Carrington, head of the Space Security Department. Liz realises Carrington was previously an astronaut on Mars Probe 6.
Carrington tells them that on the way back Mars Probe 7 hit an undetected radiation belt. Each astronaut is issued with an emergency signal, and that is what was being received at Space Control. Carrington behaved covertly because this was a security issue, and UNIT were not involved because they are a global organisation, and the Government wanted to keep it local. The Doctor doesn't believe this, and wants to see the astronauts. Carrington arranges for the astronauts to be taken away whilst he takes the Doctor, Li and the Brigadier to his facility, where he pretends to know nothing about them being taken.
Looking through notes Liz finds radiation readings - readings that are too high for a human to withstand. The Doctor surmises that the three crewmen are still in orbit. The three astronauts, whatever they are, are emitting radiation. At a new facility the astronauts are being looked after by Doctor Lennox (struck off) and Reegan, who had killed some of Carrington's men after the kidnap from the original facility.
Back at Space Control the Doctor tells Cornish about the crew, and he asks Quinlan for authorisation to send up another recovery capsule. When Quinlan, and Carrington, refuse Cornish tells them he is going to start preparations anyway. The Doctor starts to prepare Recovery 7 to go back into space as Liz received a message asking her to meet the Brigadier to investigate two bodies that had been found in a gravel pit - left by Reegan.
The message is a trick, and Liz is followed by Reegan. Liz stops and make a run for it, followed by Reegan and some other men, caught, and taken to the new facility. Liz is made to work with Lennox, but when the men guarding her go to ask Reegan for more radioactive cannisters that the astronauts need Lennox gives her a key to the door, and she locks Lennox in the room with the astronauts to make it look like an escape. She is re-captured soon afterwards after she flags down a car - belonging to Taltalian.
Taltalian confronts Reegan, and gives him instructions on how to use a machine that can give basic orders to the astronauts to give them commands that will allow them to carry out raids on selected targets. He also tells Reegan that the Doctor is close to constructing a similar machine, and that Reegan should get rid of him permanently. Reegan gives Taltalian a bomb in a briefcase.
Despite numerous obstructions the recovery capsule is close to readiness. As there are suddenly no available astronauts the Doctor tells Cornish he will take the capsule back into space. As Cornish goes to prepare tests for the Doctor Taltalian enters the room with the briefcase, and then makes an excuse about fetching information from his car. But when he arms the bomb instead of the fifteen minutes he had been told he had the bomb expoldes straight away. Taltalian took the full blast leaving the Doctor safe.
Reegan, using the controller given to him by Taltalian, orders one of the astronauts to raid the computer room at Space Control. A second astronaut is sent to kill Quinlan and destroy important documents. The Doctor had been contacted by Quinlan, and arrives moments afterwards when the astronaut is still in the room. As the astronaut is about attack the Doctor the Brigadier fires at it. The shots do no damage, but the astronaut returns back to Reegan with its mission complete.
With the death of Quinlan and Taltalian, and the attack on Space Control, General Carrington tells Cornish he forbids the launch of Recovery-7, even though he does not have the authority. He does entertain the idea of sending up a nuclear weapon instead of a person, which the Doctor does not agree with.
Back at the facility Lennox manages to bluff his way out by convincing the man guarding them that he needs more isotopes for the astronauts otherwise they will die. He makes his way to Space Control to talk to the Brigadier. Benton places Lennox in a cell to wait for the Brigadier. Reegan finds out about the escape and tells Cartwright who places radioactive isotopes inside Lennox's cell.
The Doctor prepares to go up in Recovery-7, and is annoyed that the lift off will take a further thirty minutes for the fuel and M3 to be mixed properly. As the fuel is prepared one of Reegan's men breaks into Space Control and starts to interfere with the fuel injection system. The Brigadier, performing a security check, finds an injured soldier who had been guarding the fuel systems, and returns to Space Control to tell Cornish to stop the launch - but is too late.
Recovery-7 starts accelerating too fast. The Doctor can handle G-forces better than humans, but even he is being affected, and the capsule is dangerously close to heading towards the sun. The Doctor tells them to initialise a stage one jettison earlier, and this stabilises the capsule, and the Doctor is able to link up with Mars Probe 7. At the same time another object is on a collision course with Mars Probe 7 and the capsule. The new craft links takes the capsule on board, and an alien voice tells the Doctor to leave the capsule into their craft.
The Doctor is directed to a psychedelic room where the original three astronauts are being held. They believe they are in extended quarantine at Space Control. It comes as a surprise to them when the Doctor tells them they are being held prisoner on board a spaceship. On a screen a helmeted figure appears, and the original astronauts fall into a trance.
The alien asks the Doctor what has happened to the Ambassadors, and accuses the Doctor of breaking the agreement, and threatens to destroy Earth unless they are returned. The Doctor tells the alien he knew nothing abut the agreement and tells the alien he will do all he can to return the Ambassadors. The original astronauts must remain on board until the Ambassadors are returned, and the Doctor is allowed to return to Earth.
On Earth Space Control has realised that an alien spacecraft has taken Mars Probe 7 and Recovery 7. General Carrington favours destroying the ship with atomic rockets. The Brigadier tells Cornish that he is suspicious of Carrington, believing he knows more than he is letting on. Carrington orders Reegan to kill the Doctor, and pumps gas into the decontamination ventilation system. Decontamination should take an hour, and with a few minutes left the Doctor is overcome by fumes. Reegan, wearing a mask, enters the decontamination room and kidnaps the Doctor.
Reegan takes the Doctor back to his facility. He tells Carrington that the Doctor is dead, but he isn't. After the death of Lennox Reegan is after another scientist to look after the Ambassadors. The Doctor is just happy to be reunited with Liz. Reegan tells the Doctor to build a machine that can properly talk to the Ambassadors, and the Doctor makes a list of equipment that he needs.
Carrington later visits the facility and is taken aback to find the Doctor alive. He confronts Reegan about it, and Reegan says the Doctor is the best choice to communicate with the Ambassadors. The Doctor learns that Carrington met the aliens on board an earlier Mars Probe mission when they accidentally killed one of the astronauts by touching him. Since then Carrington has been planning revenge on them. Carrington plans to show one of the Ambassadors on television, and call upon the nations of Earth to fight against them.
In the facility the Doctor builds a morse code device, and sends an SOS message that UNIT us able to pick up, whilst he also builds a device that can talk to the Ambassadors. In Space Control a message is received from the aliens demanding the release of their Ambassadors.
After UNIT receive the SOS the Brigadier prepares to go after the Doctor, but Carrington overrules him and places him under arrest. Whilst being taken away the Brigadier manages to escape and return to UNIT HQ. Unfortunately there is only a few staff at UNIT HQ, and no transport - apart from the Doctor's car, Bessie. The Brigadier, Benton, and a few other soldiers manage to get into the facility where the find the Doctor, Liz and Reegan, and two of the Ambassadors.
In order to stop Carrington, who has taken over Space Control, the Doctor uses the two Ambassadors. They are impervious to Carrington's soldiers' bullets, and they are able to gain entry, followed by the Doctor, Liz and UNIT. As Carrington begins to broadcast the nation the Brigadier, with the help of the Ambassadors, interrupts, and Carrington is arrested. As Carrington is taken away by UNIT Cornish prepares to exchange the Ambassadors with his three astronauts.
Regular castBrigadier Lethridge-Stewart: Nicholas Courtney; Liz Shaw: Caroline John; Sergeant Benton: John Levene;
Guest castProfessor Ralph Cornish: Ronald Allen; General Carrington: John Abineri; Charles Van Lyden: Ric Felgate (1,2,reprise 3,6); Doctor Bruno Taltalian: Robert Cawdron (1-2,4); John Wakefield: Michael Wisher (1-2,7); Grey: Ray Armstrong (1-2); Miss Rutherford: Cheryl Molineaux (1-2); Collinson: Robert Robertson (1-2); Sir James Quinlan: Dallas Cavell (2-4,reprise 5); Control Room Assistants: Bernard Martin (2), Joanna Ross (5-7), Carl Conway (5-6); Dobson: Juan Moren (2); Corporal Champion: James Haswell (2); UNIT Sergeant: Derek Ware (2); Reegan: William Dysart (3-7); Doctor Lennox: Cyril Shaps (3-5); Alien Astronauts: (all 3-7 - uncredited 6) Ric Felgate, Steve Peters, Neville Simons; Professor Heldorf: Gordon Sterne (3); Masters: John Lord (4); UNIT Soldier on Main Gate: Max Faulkner (3-7 - uncredited for 6); Johnny Flynn: Tony Harwood (5); Private Parker: James Clayton (5); Technician (Peterson): Roy Scammel (5); Alien Space Captain: Peter Noel Cook (6-7); Aliens' Voices: Peter Haliday (6-7); Joe Lefee: Steve Peters (6); Frank Michaels: Neville Simons (6); Private Johnson: Geoffrey Beevers (5,7 - uncredited 5);
Uncredited cast: Assistant: Sue Borne (3,5); Military Policemen: Royston Farrell (7), Tom O'Leary (7); Cameramen: Roy Reeves (7), Les Shannon (7); Heavies: Alf Joint, Barry Kennington, Dinny Powell, Gordon Stothard; Control Room Assistants: Roy Brent, Derek Chafer, Les Conrad,Stella Conway, Barbara Faye, Paul Gilman, David J Graham, Dennis Haywood, Dianna Holt, Tony Laing, Roger Minnis, Caroline Mylon, Wilma Oswald, Rod Peers, Clive Rogers, Lindsey Scott, Keith Simon, Sheila Vivian; Soldiers: David Aldridge, Roy Brent, Geoff Brighty, Derek Chafer, Alan Chuntz, Les Conrad, Ron Conrad, Ron Gregory, Steve Kelly, Tom Laird, Stewart Myers, Rod Peers, David Pike, Doug Rae, Clive Rogers, Jo Sentos, Keith Simons, Steve Smart, Terry Walsh; Technicians: Max Diamond, Pat Gorman, Nick Hobbs, David Joyce;
|BBC 1||265||Episode One||Sat 21 March 1970||5:15 pm - 5:40 pm||7.1M||60th|
|BBC 1||266||Episode Two||Sun 29 March 1970||5:15 pm - 5:40 pm||7.6M||59th|
|BBC 1||267||Episode Three||Sat 4 April 1970||5:20 pm - 5:45 pm||8.0M||60th|
|BBC 1||268||Episode Four 1||Sat 11 April 1970||5:45 pm - 6:10 pm||9.3M||46th|
|BBC 1||269||Episode Five||Sat 18 April 1970||5:15 pm - 5:40 pm||7.1M||57th|
|BBC 1||270||Episode Six||Sat 25 April 1970||5:15 pm - 5:40 pm||6.9M||70th|
|BBC 1||271||Episode Seven||Sat 2 May 1970||5:15 pm - 5:40 pm||5.4M||80th|
1: Originally scheduled for 17:15
Marlow Wier, Mill Road, Marlow; North Thomas Gas Works, Southall; Spade Oak Quarries, nr. Little Marlow, Bucks; Wycombe RDC Sewage Purification Works, Little Marlow, Bucks;
Television Centre Studio 1; Television Centre Studio 3; Television Centre Studio 4;
Bloopers and mistakes
When the Doctor goes up in the rocket to dock with the Mars probe, he tells the space station controller that he can withstand more G force than normal people, so they can use more M3 fuel to make the trip faster. The controller declines saying the risk of the rocket exploding is too great. However, later when the aliens are working with the Doctor and he is sending them back to their ship on board a rocket, the Doctor suggests using pure M3 fuel as the Ambassadors will not be affected by G force. Why was there no concern any more about the second rocket exploding?
When Lennox is being chased up the stairs by the Alien, Reegan is knocked away. The Alien starts to collapse and Reegan jumps to get out of his way, hitting a "brick" wall that shakes quite a bit.
Episode 1: In the scene where Van Lyden is sitting in the spaceship, as viewed on the monitor screen at space control, Van Lyden says something like "Beginning rotation now," and the image on the screen rotates. Assuming this image comes from a camera inside the shuttle, surely this would mean the ship rotated but the camera didn't, unless the camera was outside in space (not a very satisfactory explanation!).
Episode 1 & 7: In episode 1, we see a shot of the launch control room, which has a high ceiling. At the very end of episode 7, we see another such shot, only they used the wrong backdrop this time. Suddenly the room has the same roof as the rocket launch site seen in episode 5.
Episode 4: When Reegan goes into the cell to help the dying Ambassador, one of them touches him and he flies against the wall. But when the Ambassadors touch anyone else, they are killed!
Episode 4: Listen out for Taltalian's amazing changing accent in his car when he confronts Liz!
Episode 4 & 6: The same guard (stuntman Max Faulkner) who is killed by the Ambassador whilst at the main gate in episode 4 is alive and well in episode 6.
Notes and trivia
This story has a unique way of handling the titles; the story title, writer credit and episode number come up in a separate title sequence after the recap.
Episodes Two to Seven are held only as film prints and NTSC recordings (a fault on the colour copy has prevented successful restoration as with Doctor Who and The Silurians)
The Invaders from Mars; Carriers of Death; The Ambassadors;