Doctor Who: The Keys of Marinus

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The Keys of Marinus is the fifth serial in the original Doctor Who series. It was first broadcast on BBC TV/BBC1 in six weekly parts from 11 April to 16 May 1964. It was written by Terry Nation and directed by John Gorrie. It stars William Hartnell as the Doctor, Carole Ann Ford as Susan Foreman, William Russell as Ian Chesterton, and Jacqueline Hill as Barbara Wright.

It is a science fiction adventure structured like a quest, with the TARDIS crew traveling to different locations on the planet Marinus to find the four scattered keys needed to reactivate a powerful machine called the Conscience of Marinus.

Episode 1: The Sea of Death

The TARDIS lands on a tiny island of glass, surrounded by a sea of acid. Stones hiss and melt when they touch the water. The travellers spot a strange craft beached on the shore and realise they are not alone. Moving inland, they find a glass pyramid that rises from the island. Inside, corridors are silent, and Barbara is briefly separated from the others.

A robed man appears. He is Arbitan, guardian of the Conscience of Marinus, a vast machine that once kept peace by dampening evil thoughts. Now the Voord, masked invaders, seek to control it. To stop them, Arbitan scattered five micro-keys across the planet. He begs the Doctor, Ian, Barbara, and Susan to retrieve them so he can restore it.

The Doctor refuses the mission, but Arbitan surrounds the TARDIS with an energy barrier, leaving them trapped on the island. Outside, a Voord tries to seize the ship but the acid sea drives it back. With no choice, the travellers accept Arbitan’s quest. He gives them travel dials. One by one, they activate the devices and vanish to begin the search. Their first destination looks safe and beautiful, but unseen dangers are already waiting for them.

Episode 2: The Velvet Web

The travellers arrive via the travel dials in a shining city called Morphoton. Attendants greet them with rich food, soft beds, and beautiful clothes. The people praise their unseen Masters and promise every wish can be granted. The Doctor, Ian, and Susan fall under a calm, dreamy mood.

Barbara also smiles, but during the night the small disc used in her ‘welcome’ slips from her forehead. She wakes and sees the truth: the rooms are bare, the food is rotten, and their fine clothes are rags.

Barbara is seized by guards and taken before the Masters: living brains in glass jars called the Morpho. They use hypnotic devices to enslave the city. With courage and luck, Barbara smashes the equipment and destroys the Morpho. The spell over Morphoton breaks. The attendants see what has been done to them.

Among the loot Barbara finds the first micro-key to the Conscience of Marinus. Two young citizens, Altos and Sabetha, recover their memories and join the quest to find the rest. The Doctor decides to go ahead alone to the next location and meet them later. Using their travel dials, the friends jump away from Morphoton to continue the search for the remaining keys.

Episode 3: The Screaming Jungle

The travellers (Ian, Barbara, Susan, Altos and Sabetha) arrive by travel dials in a humid jungle that seems to breathe and wail. Vines lash like whips, and pods shriek when touched. They search for Darrius, a scientist who hid a micro-key for Arbitan. Inside a crumbling building overgrown by roots, they find Darrius mortally wounded. With his last breath he warns them that the place is full of traps and gives a broken clue to the key’s location.

Following the clue, they move through corridors where stone faces spit darts and floors give way. Barbara is separated by a sliding wall and must puzzle out a series of devices to survive. She discovers an idol that appears to hold the key, but taking it triggers a crushing mechanism.Ian rescues her and realises it was a decoy. Reading Darrius’s notes and labels, Barbara pieces together the real message and locates the true key hidden among plants in the laboratory.

As vines close in and the building begins to tear itself apart, the group fights their way back to the open air. With the second micro-key safely in hand, they use their travel dials and jump away: to a place of snow and ice.

Episode 4: The Snows of Terror

Ian, Barbara, Susan, Altos and Sabetha arrive by travel dials in a frozen wilderness. Snow blinds them, wind cuts, and wolves howl in the distance. Susan becomes separated and is found by a fur-clad trapper named Vasor, who brings her to his hut.

The others follow for fire and shelter. Vasor seems helpful, but he secretly steals their travel dials and hides them. He urges Ian and Altos to go to a nearby ice cave to seek the next micro-key, while Barbara and Sabetha remain behind.

Ian and Altos cross a broken rope bridge and enter glittering tunnels. They reach a chamber where motionless armoured figures, the Ice Soldiers, stand guard. Beyond them burns a small flame; in the ice behind it lies the key. When the key is taken, the ice melts and the soldiers begin to move. Ian and Altos escape as cave shudders and the rope bridge snaps.

At the hut, Vasor turns threatening and tries to keep the women. Barbara tricks him, finds the dials, and she and Sabetha flee into the snow. Ian returns, confronts Vasor, and drives him into the wolf-haunted night. Reunited, the friends secure the third key and jump to the city of Millennius.

Episode 5: Sentence of Death

The travellers arrive in the city of Millennius to claim another micro-key from a secure vault. Ian is sent to collect it, but an alarm sounds. Guards rush in and find Ian beside a dead official and an empty box holding only a fake key. He is arrested at once. In Millennius, the law assumes guilt until innocence is proven, and Ian faces a swift death sentence unless the real thief is found.

The Doctor returns and offers to act as Ian’s advocate. He persuades the court to grant a short delay to investigate. Working with a fair-minded city investigator, the Doctor, Barbara, Susan, Altos, and Sabetha begin piecing together clues: a clumsy counterfeit key, a series of false alibis, and signs of an organised theft ring that has been hunting the same prize.

Witnesses are scared into silence, and one informant is killed before he can speak. Susan is lured by a threatening voice, but Barbara traces the sound to a nearby room and proves it was a trick meant to frighten them away. The team narrows the suspects and exposes part of the conspiracy, but the missing key and the true mastermind remain hidden. As the court’s deadline approaches, Ian’s life hangs in the balance.

Episode 6: The Keys of Marinus

Ian’s trial continues in Millennius. The Doctor, Barbara, Susan, Altos, and Sabetha follow new clues, expose the thieves’ plot, and prove that Ian was framed. The real criminals are arrested, and the genuine micro-key is recovered. With all five keys now gathered, the friends use their travel dials to return to the glass tower on Marinus.

Inside, they are greeted by “Arbitan,” who demands the keys at once. Something feels wrong. Barbara notices small details that do not fit, and the group realises this is not the guardian at all but Yartek, leader of the Voord, disguised in Arbitan’s robes. The Voord have seized the tower, and the real Arbitan is dead. Yartek plans to power the Conscience of Marinus and rule the planet by controlling every mind.

The travellers must choose: hand over the keys and doom Marinus, or stop the machine forever. Using a counterfeit key taken in Millennius and a quick bit of misdirection, they trick Yartek into activating the Conscience in a way that destroys it. The tower erupts; Yartek and his Voord are killed, and the machine’s rule ends for good. Altos and Sabetha stay to rebuild their world. The Doctor, Ian, Barbara, and Susan depart in the TARDIS.

Themes

As television, The Keys of Marinus is a lively “road movie” in six parts, each stop a new puzzle. The story sometimes shows its budget and its quick production, and a few obstacles are solved very simply. Many fans rate it above average for early Season 1, not as iconic as The Daleks, but more varied and energetic than some longer tales.

It also threads the series’ past and future. Coming after Marco Polo, it brings the moral focus of the historicals into a science-fiction frame: should any machine dictate right and wrong?

The answer, no, foreshadows later stories that challenge easy control and easy peace. The Voord, with their black suits and amphibious craft, feel like early sketches of later masked foes, while the travel-dial structure points forward to later “quest” seasons and anthology-style adventures.

The closing beat sends the team from a shattered tower to a sacred tomb, leading into The Aztecs, where the show will again test the limits of interference, respect, and responsibility before the wheeze-groan takes them on.

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This is a chapter from Craig Hill’s book “Doctor Who – The First Doctor”, chronicling every episode featuring the First Doctor. It is available on Amazon.

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To view the list of other Doctor Who serials, please click this link

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