The Keys of Marinus
The Doctor and his companions must prove Ian's innocence after he's framed for murder, while also stopping the true culprits from stealing a powerful key that could give them control over the entire planet of Marinus.
Following Ian's wrongful arrest and trial for the murder of Ayden, the Doctor and his companions, Barbara and Susan, work to uncover the truth and expose the real killers. Barbara pieces together that Kala, Ayden's wife is guilty, after she reveals knowledge of their conversation with Susan. Kala's arrest doesn't exonerate Ian, as Kala falsely accuses him of being her accomplice. The Doctor deduces that the plot is centered around a key hidden within a mace, leading them to set a trap.
The Doctor catches Eyesen, the prosecutor, attempting to steal the mace containing the key. With Ian freed, the group uses their wrist straps to travel to the city of Millenius, where they were headed before Ian's arrest. They find Altos being interrogated by Yartek, who has taken over from Arbitan and is seeking the final key required to control the Conscience machine, so he might dominate the planet. The travelers, despite some unease, continue to Arbitan, hoping to retrieve the final micro-key, but discover Arbitan has died and been replaced by Yartek, who is impersonating him.
After realizing the deception, Ian gives Yartek a fake key and rejoins the Doctor, Barbara, Susan, Altos and Sabetha to try and put an end to Yartek's evil plans. He reveals that Barbara has the real one. They try to escape, but the Doctor, Altos and Sabetha are captured. Yartek plans to use the machine to enslave them all. Learning that Arbitan is dead further motivates them to prevent Yartek from succeeding. They escape the cell they were in. Ian and Susan are able to deceive Yartek long enough for the others to arrive, rescue them, and replace all the keys. Sabetha and Altos escape while the Doctor and his companions return to traveling in the TARDIS.
Events in This Episode
The narrative beats that drive the story
Barbara deduces Kala's complicity in Ayden's murder, realizing Kala's knowledge of their conversation with Susan could only come from direct involvement. With Altos and Sabetha, Barbara confronts Kala, freeing Susan and apprehending the killer. The Doctor, initially despondent over Ian's impending execution, receives Barbara's call, confirming Kala's guilt. However, Kala's subsequent confession falsely implicates Ian as her accomplice, ensuring his execution proceeds. Susan's recollection of a mysterious phone call, mentioning a "key," sparks the Doctor's realization that the murder is part of a larger scheme. He devises a trap, correctly deducing the true villain will attempt to steal the key from the mace held as evidence. Prosecutor Eyesen, revealed as the conspirator, falls into the trap, caught red-handed. Ian is immediately freed, his innocence proven. The Doctor explains the plot: Kala and Eyesen intended to steal and sell the powerful key. With Ian exonerated and the initial threat neutralized, the companions prepare to continue their journey to Millenius, using their unique wrist straps for instantaneous travel, leaving the local authorities bewildered by their sudden disappearance and the unfolding events. This act successfully resolves the immediate danger to Ian while propelling the narrative towards the larger planetary conflict.
The scene opens with the Doctor in quiet despair after Ian’s conviction, his grief hardening into subtle accusation toward Eyesen, the prosecutor. Barbara’s phone call interrupts this moment, revealing Kala’s …
The Doctor, disheartened by Ian’s impending execution, remains in the reception area to uncover new evidence. When Susan recalls a cryptic phone conversation—where an unknown man instructed Kala to kill …
The Doctor orchestrates a trap to expose Eyesen as the mastermind behind the conspiracy to steal the key, clearing Ian’s name in the process. After Barbara reveals Kala’s confession implicating …
The Doctor and his companions—Barbara, Susan, and Ian—prepare to leave the reception area after successfully clearing Ian’s name and exposing the conspiracy behind Ayden’s murder. The Doctor orchestrates a trap …
Upon their arrival in Millenius, the companions encounter a new, insidious threat. Altos, having traveled ahead, is discovered under interrogation by Yartek, a menacing frog-like creature who has usurped Arbitan's authority and now impersonates him. Yartek coldly declares Arbitan dead, revealing his ambition to seize control of Marinus through the powerful Conscience machine, for which he requires the final micro-key. Sabetha, also captured, attempts to protect Altos by feigning indifference, but Yartek's ruthless threats force Altos to divulge that the Doctor possesses the crucial key. Meanwhile, the Doctor, Ian, Barbara, and Susan arrive in the city, immediately sensing an unsettling atmosphere and the absence of Altos and Sabetha. Their unease intensifies as Yartek, having already inserted four micro-keys into the Conscience machine, awaits the fifth to complete his dominion. A confrontation with a lurking Voord confirms the pervasive danger. Recognizing the escalating peril, the companions decide to split up: Ian and Susan venture to find Arbitan, unaware of his demise and Yartek's deception, while the Doctor and Barbara set off to locate Altos and Sabetha. Ian is entrusted with the real key, unknowingly carrying the very object Yartek desperately seeks, thus setting the stage for a perilous confrontation.
The Doctor and Barbara locate Altos and Sabetha, bound within a cell, and swiftly free them. Altos reveals the full, dire scope of Yartek's plan: to use the Conscience machine to enslave all inhabitants of Marinus, extinguishing their free will, including their very impulse to leave the planet. Simultaneously, Ian and Susan, still under the illusion that Yartek is Arbitan, enter the control room. Yartek, maintaining his disguise, demands the key. With quick thinking, Ian presents Yartek with the *fake* key, a replica previously found by Barbara. Unaware of the deception, Yartek accepts it, believing his plan for absolute power is imminent. Ian and Susan soon realize Yartek's true identity and the gravity of their situation. They reunite with the Doctor, Barbara, Altos, and Sabetha, where Ian clarifies his ruse, revealing Barbara still holds the genuine key. Altos then explains the fake key's catastrophic potential: inserting it into the Conscience machine will cause a massive explosion, destroying the device and the entire building. A frantic race against time ensues as the companions attempt to escape the collapsing structure. Yartek, oblivious to his impending doom, inserts the fake key, triggering the machine's destruction. The Doctor shares a poignant moment with Sabetha, reflecting on her father Arbitan's legacy and the inherent dangers of machines controlling humanity. With Yartek defeated and the threat neutralized, Altos and Sabetha resolve to return to Millenius to rebuild. The Doctor, Ian, Barbara, and Susan bid them farewell, re-entering the TARDIS to dematerialize, embarking on their next adventure, leaving behind a world saved from tyranny.
In the control room, Yartek—disguised as Arbitan—confronts Ian and Susan, his urgency for the key revealing his desperation and the true stakes of the theft. His claim of radiation poisoning …
In the Control Room, Ian and Susan execute their carefully orchestrated deception by presenting Yartek with the forged micro-key, which he eagerly accepts as genuine. Yartek, disguised as Arbitan and …
In a high-stakes confrontation, the Doctor and companions uncover the full scope of Yartek’s conspiracy: he plans to use the stolen machine and the final micro-key to enslave Marinus. Ian …
The Doctor’s demand to destroy the stolen key backfires when Ian reveals he gave Yartek a fake—unaware it’s rigged to detonate the Conscience machine and the entire building. Altos’s horrified …
Outside the TARDIS, the Doctor seizes a private moment with Sabetha to address her grief over Arbitan’s death, reframing her father’s legacy as a call to action rather than a …
Outside the TARDIS, the Doctor shares a private, emotionally charged farewell with Sabetha, framing Arbitan’s death as a call to preserve humanity’s values over machine control. His words—‘Machines can make …
As the Doctor prepares to depart Marinus with his companions, Ian—still grappling with the weight of the fake key he withheld from Yartek—seeks Barbara’s counsel before deciding to surrender it …