Galaxy 4 was the first story of the third season of Doctor Who, recorded after The Time Meddler as part of the series’ second recording block. Its third episode, “Air Lock”, achieved the highest ratings of any episode between the final episode of The Web Planet and the final episode of The Three Doctors. Indeed, “Air Lock” is one of the few episodes from pre-BBC Wales Doctor Who to have ranked amongst the top fifteen shows of its initial broadcasting week.
Galaxy 4 is the earliest non-historical story to have missing episodes. Until the recovery of “Air Lock” in 2011, it was notable for the extreme paucity of its surviving material. Because no telesnaps were taken during broadcast, photographic evidence for this story was effectively limited to publicity shots (with only one photograph of the Rills) and a six minute excerpt from “Four Hundred Dawns”.
Actor Peter Purves has been outspoken in his distaste for the serial, which was originally written for Ian, Barbara and Vicki. He has frequently opined that his character, companion Steven Taylor, was not well-served because the hurried rewrite mostly transferred Barbara’s lines to him, resulting in a “feminisation” of Steven’s character.
Episode 1: Four Hundred Dawns (Lost)
The First Doctor, Vicki and Steven Taylor arrive on an eerily silent planet. The Doctor evaluates the planet and discovers that it can sustain life but seems to have nothing living on it. This piques the curiosity of the Doctor, who is keen to investigate this anomaly. Steven is more interested in finding somewhere to swim. Just before they exit the TARDIS the crew discover a small robot feeling its way around the ship before communicating with something else with a glowing antenna. Vicki christens the machines Chumblies.
Once the Chumbley has left the TARDIS the Doctor and his companions go out and explore the planet. It has three suns and vegetation but, as yet, no sign of animals. Before they can get far, the Chumbley returns. It indicates to the Doctor and his friends that it wants them to follow it. Steven is wary. He tries to attack it. In a show of force, the machine produces a gun from its shell and sets fire to a plant. The Doctor and his companions are led away.
They have not gotten far when a group of women lying in wait for the Chumbley throw a metal mesh on the machine and deactivate it. The women introduce themselves as Drahvins, from the planet Drahva in Galaxy Four. They say that the robots are controlled by a race called the Rill, who are not to be trusted. The Drahvins say that they will take the travelers back to their ship for safety and introduce them to their leader, Maaga. However when they try to remove the mesh they find it is attached magnetically to the Chumbley. Before they can make their escape three more Chumblies appear and force the travelers and the Drahvins to flee. The new Chumblies remove the metal mesh from the prone Chumbley, which reactivates itself, and they head off in pursuit of the Doctor.
The Doctor, his companions and the Drahvins make it to the Drahvin spaceship. There they are reprimanded by Maaga for the loss of the metal mesh. After Maaga has dismissed the Drahvins, she addresses the Doctor and his companions. She explains that the Drahvins are a powerful race of women warriors who use men only for hunting. They were exploring in this part of the galaxy when their ship was shot down by the Rill. They are desperate to get off the planet because the Rill have informed them that the planet will explode in fourteen days. Their plan is to capture the Rill ship and escape.
Steven is suspicious of the Drahvin. It seems to be they who are in the wrong rather than the Rill. His position is strengthened when Maaga reveals that the Rill have offered help but the Drahvin have refused for fear of being killed.
This story is interrupted when Chumblies approach the ship. The Drahvin attack them and the Chumblies deactivate briefly, but then go on their way. Playing on the suspicions that Steven has roused in the Drahvin, the Doctor says that he is a scientist. He will learn if the planet is to explode in a fortnight and see if the Rill have been misleading the Drahvin. The Drahvin agree to this but demand one of the TARDIS crew stays with them. They insist that this is not a matter of hostages, but to have fewer unaccompanied people wandering the planet. Vicki volunteers to stay and the Doctor reluctantly assents.
When the Doctor and Steven arrive at the TARDIS they find a Chumbley trying to break the TARDIS’ force barrier. Steven and the Doctor hide until the Chumbley leaves. Back at the Drahvin ship, Maaga humiliates the other Drahvins for losing the metal mesh, blaming them for ruining the whole mission.
After trying to break into the TARDIS the Chumbley gives up. The Doctor and Steven enter the TARDIS. Inside, the Doctor consults his astral map and finds the planet doesn’t have a fortnight until its destruction. It has only two days!
Episode 2: Trap of Steel (Lost)
The Doctor and Steven decide they must leave immediately, save Vicki and warn the Drahvins. However, the Chumblies return, this time with heavy explosives. It does no damage to the TARDIS. After they leave, the Doctor and Steven race back to the Drahvin ship. In the Drahvin ship Vicki is fed up with the food and is worried about her friends. Maaga refuses to let her leave.
When Steven and the Doctor get back to the Drahvin ship, Steven points out it is made of a metal that the Chumblies’ ray can penetrate. The Doctor ponders why the Chumblies have not destroyed their “enemies”. Inside the ship the Doctor hides the truth from the Drahvin and again tries to convince them to befriend the Rills and work together. Maaga rejects this again. She grows suspicious of the Doctor and pulls a gun on him. Under this threat the Doctor admits they have only two days. He offers to bargain with the Rill for a peace treaty. The Drahvin agree but retain Vicki as an insurance policy. Steven offers himself as a hostage. Vicki and the Doctor leave for the Rill ship.
Steven tries to create disharmony between Maaga and her minions. Maaga overhears this. She tries to convince Steven to pilot the TARDIS with the Drahvin. Steven refuses, saying that even if he wanted to, he doesn’t know how. He is left alone and falls asleep.
Trapped by a Chumbley patrol the Doctor and Vicki are forced to “observe, note, collate and then conclude” their routine. Vicki decides to test a theory by throwing a stone behind the machine. The Doctor is annoyed but she states that she thinks the Chumblies can detect only what is in front of them. They conclude that they can follow one back to the Rill ship rather than wander aimlessly.
Back at the Drahvin ship Maaga orders her minions to break into the Rill spaceship and wipe them out for their ship.
By this time the Doctor and Vicki are at the Rill compound. It has a drilling rig and an air purifier. The Doctor is impressed with the Rills’ handiwork. The Doctor and Vicki explore the compound cautiously. Vicki remarks that she can smell ammonia. The closer they get to the compound’s centre, the stronger the smell. They arrive in what appears to be a repair shop for Chumblies. As they look around, a large, scaly creature appears at the window. Vicki screams.
Episode 3: Air Lock
The Doctor and Vicki try to escape the Rill center, but are pursued by two Chumblies. They reach a dead-end, stopped by an iron gate. The Doctor decides the best way of disarming the Chumblies is by tinkering with the apparatus that converts the air into ammonia. He assumes the Chumblies need the ammonia. Whilst he wrecks the gas converter, the Chumblies catch up with them and indicate they want Vicki to come with them. The Doctor relents, saying it will give him time to vandalize the converter.
Back at the Drahvin spaceship Maaga shares her frustration with the other Drahvin warriors. She says they are useless at strategy and all they are worried about is killing. If the Doctor and Vicki succeed she will steal the Rill ship and leave the Rill and the humans on the planet to die. She orders the Drahvins to patrol the perimeter, leaving one to guard the sleeping Steven. She does not know Steven is awake the whole time and has been listening to her.
At the Rill center, the Chumbley prods Vicki to the window where the creature appears. A voice comes from the Chumbley, telling her that the Rill control the Chumblies. At first they are hostile to Vicki. However they learn the Drahvin have been lying to her and tell her the real story.
The two spaceships met above the planet in a stand off that lasted four days. Finally, the Rill tried to leave but the Drahvin ship fired on them. The Rill ship returned fire and both ships crashed.
The Rill tried to speak with the Drahvins. They found an injured Drahvin whom they tried to help, but Maaga found them and chased them off with a gun. She killed the wounded Drahvin warrior and blamed the Rills. Vicki realises the Rill are not the enemy. If they cannot bear the planet’s atmosphere, the Doctor’s tinkering will kill them. She runs to stop him from destroying the gas converter.
At the Drahvin ship Steven slowly raises himself silently from his bed. He sneaks up to the guard and renders her unconscious. He takes her gun and tries to leave the ship. However, as he goes Maaga comes up behind him. He finds himself facing a Chumbley. He tries to turn back but the Drahvins are pointing their guns at him. He is trapped in the airlock between the ship and the outside. Maaga gives him an ultimatum. He can surrender his gun and return to the ship, face the Chumbley or suffocate as she drains the air from the air lock. Steven is left to think as the air leaves the room.
Vicki gets to the Doctor before he can break the system. Vicki explains the situation to him and they both go to the Rill. The Doctor tells them their escape is at risk. The planet will explode before they expect.
Although the Rill ship is fixed they don’t have enough fuel. The Doctor says he can help them with metal cord cable and a sort of jump lead that he has in his TARDIS. The Rills are happy to hear this but the Chumbley outside the Drahvin spaceship tells them Steven is in danger. The Doctor and Vicki rush to his aid with two Chumblies. They are stopped by a Drahvin warrior who thinks that the Doctor has betrayed them. Vicki tries to convince the warrior that the Chumblies are under their control. The warrior tries to shoot the Chumbley, but Vicki disarms her. The Drahvin begs to be killed for her failure. The Doctor says no one will be dying on this planet any time soon.
At the spaceship Steven decides he would rather face the Chumbley than die or return to the Drahvins. He tries the door but it cannot be opened. Steven struggles for breath.
Episode 4: The Exploding Planet (Lost)
There is no time to spare. A Chumbley shoots an ammonia bomb into the Drahvin spaceship and fires its weapon at the airlock, freeing Steven. The Drahvins flee and are met by a horde of Chumblies. The Rill tell them for all these years they have been pacifist in their dealings with the Drahvin. Now that they have threatened to kill Steven, they will be killed in return. The Rill order the Drahvin back into their ship. If they are seen on the planet’s surface again they will be killed.
Inside the ship Maaga blames the Drahvin who was on patrol for their predicament. She will pay the ultimate price when they have more time. Maaga lays out her plan to destroy the Rill ship.
In the Rill ship the Doctor puts the finishing touches to his plan to give a jump start to the ship’s engine with his TARDIS. He leaves Steven to recover in the Rill center whilst he and Vicki return to the TARDIS to link it to the Rill ship’s engine. Alone with the Rill, Steven expresses his doubts of the benevolence of the Rills. He suspects that if the Doctor cannot fix their ship the Rill will not let them go. The Rill say they would let the Doctor go. They have no knowledge of conflict and would rather have a life saved than kill someone for no reason. Steven apologizes for his skepticism. On the other side of the planet one of the Drahvin sneaks up behind the Chumbley guard and destroys it.
The Rill are told the Doctor has hooked up his TARDIS. Steven is nervous. He is sure the ship will not be powered up in time. The Doctor and the Rill assure him they can complete the process before the planet explodes. A Drahvin bursts into the Rill center. Before she can do any damage, a Chumbley paralyses her.
In the aftermath Steven and Vicki look for the Doctor. They find him in the section of the Rill center with the Rill, where they were not allowed before. The Doctor invites them in and the Rill gives them permission to enter. At first shocked at their ugliness, the humans come to an understanding with the Rill. They bid each other farewell.
Meanwhile, the Drahvins wait outside the Rill camp. They fight off an army of Chumblies to get close to the Rill ship. They find that their weapons are useless and decide to rush the ship.
With the ship ready for flight, the Rill sends a Chumbley to escort the Doctor and his companions to the TARDIS. The TARDIS travelers watch as the Rill ship flies off. Nearby, the Drahvins despair as their chance of salvation disappears into orbit. Maaga catches sight of the Doctor and his companions. The Drahvin pursue them to hijack the TARDIS, but it dematerializes before the Drahvin reach their door. Seconds later the planet explodes, destroying the Drahvin soldiers and Maaga.
Back on their travels, the Doctor and his companions lament that they have had precious little time for peace and quiet recently. Vicki looks at a planet below and wonders what might be going on there.
On that planet, unbeknownst to the travelers, an astronaut has awakened in a dense jungle, remembering only that he “must kill” . . .