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Season guide

Doctor Who: The Key to Time

26 episodes Premiered Sep 2, 1978 Updated Sep 25, 2026

This season saw the introduction of the Black and White Guardians as well as the companion Romana, who became only the second female Time Lord companion since Susan. This season is sometimes colloquially known as The Key to Time season after the story arc involving the Key to Time. Although not the first season to consist of linked stories (Season 8 in 1971 was the first, as all the stories that year featured the Mas

Previously on Doctor Who

Season 16 Lore Primer

Key plot threads, lore context, and character stakes you need to remember before diving into this season.

  • ⚡ Directly follows the overarching narrative developments of Doctor Who Season 15.
  • ⚡ Faction dynamics and core character alliances shift under escalating external stakes.
  • ⚡ Crucial mysteries introduced previously reach key turning points and narrative reckonings.
  • ⚡ Sets up serialized story arcs that build directly toward the climactic season finale.

Season overview

This season saw the introduction of the Black and White Guardians as well as the companion Romana, who became only the second female Time Lord companion since Susan. This season is sometimes colloquially known as The Key to Time season after the story arc involving the Key to Time. Although not the first season to consist of linked stories (Season 8 in 1971 was the first, as all the stories that year featured the Master), it was the first to be recognised as having a series long arc. Although multi serial arcs would occur again, such a full- season experiment wouldn't be attempted again until Season 23. The arc has a number of similarities to the Season 1 story The Keys of Marinus. The storyline was originally proposed for Season 15, but it required more planning.

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Season 16 Episodes

Episode Guide

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Season 16 Progress Shield

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Binge Efficiency Engine

Season 16: Filler vs. Essential Canon

Filter episodes by narrative weight. Focus on essential mytharc and skip standalone side quests.

12%
88%
Mytharc (3): Crucial lore & season climaxes
Core (23): Character development & subplots
Side Quest (0): Standalone / filler
S16·E1 Mytharc

The Ribos Operation (1)

Sep 2, 1978 · 25 min

The Magellanic Clouds, the planet Ribos, an unknown time. Ordered by the White Guardian to collect the pieces of the omnipotent Key to Time, The Doctor, K-9 and his new assistant R

S16·E2 Core

The Ribos Operation (2)

Sep 9, 1978 · 25 min

Trying to obtain the first segment of the Key to Time, the Doctor and Romana are swept up in an elaborate con. The target – the homicidal Graff Vynda K.

S16·E3 Core

The Ribos Operation (3)

Sep 16, 1978 · 25 min

Prisoners of the maniacal Graff Vynda K, the Doctor and Romana must break out and pursue the first segment – even as Unstoff takes it into the most dangerous place on Ribos.

S16·E4 Core

The Ribos Operation (4)

Sep 23, 1978 · 25 min

Trapped in the catacombs between a mad warlord and ravenous monsters, the Doctor and Romana work desperately to obtain the segment of the Key to Time - and escape alive.

S16·E5 Core

The Pirate Planet (1)

Sep 30, 1978 · 25 min

Planet Zanak, unknown time. The Doctor and Romana are seeking the planet Calufrax where the second segment waits. They are in the right place and the right time… but on the wrong p

S16·E6 Core

The Pirate Planet (2)

Oct 7, 1978 · 25 min

The Doctor begins to investigate the mysteriously wealthy planet Zanak. Mentiads, a deranged Captain, strange omens, miraculous mines – what does it all mean? And what does it have

S16·E7 Core

The Pirate Planet (3)

Oct 14, 1978 · 25 min

The Mentiads take the Doctor, Romana and Kimus to a reunion with K9 and Mula, where they set about trying to defeat the Captain.

S16·E8 Core

The Pirate Planet (4)

Oct 21, 1978 · 25 min

The Captain and Xanxia work toward their secret goals. Both depends on the pirate planet consuming one more victim - Earth.

S16·E9 Core

The Stones of Blood (1)

Oct 28, 1978 · 25 min

England, the late 1970s. The Doctor and Romana arrive in search of the third segment. But the Tracer readings are erratic and something ominous is happening with an ancient stone c

S16·E10 Core

The Stones of Blood (2)

Nov 4, 1978 · 25 min

The quest for the Third Segment has landed the Doctor and Romana in the midst of a druidic cult centred on a stone circle. But the stones are not what they seem, and somewhere out

S16·E11 Core

The Stones of Blood (3)

Nov 11, 1978 · 25 min

Chased by blood-thirsty stones, the Doctor must find a way to rescue Romana. What awaits him in the theoretical absurdity of hyperspace?

S16·E12 Core

The Stones of Blood (4)

Nov 18, 1978 · 25 min

Facing a sentence of death from merciless justice machines, the Doctor must play for time while Romana tries to discover just who Vivian Fey really is.

S16·E13 Core

The Androids of Tara (1)

Nov 25, 1978 · 25 min

Arriving on Tara, Romana locates the fourth segment of the Key to Time with ease. But getting it away proves more difficult, as she is captured by the scheming Count Grendel who wa

S16·E14 Core

The Androids of Tara (2)

Dec 2, 1978 · 25 min

The Doctor must employ a desperate gambit to keep the evil Grendel off the throne. And the Count has a new pawn to play - Romana.

S16·E15 Core

The Androids of Tara (3)

Dec 9, 1978 · 25 min

The battle for control of Tara turns into a duel of wits between the Doctor and Grendel. But the Count shows he has more treacherous tricks up his sleeve.

S16·E16 Core

The Androids of Tara (4)

Dec 16, 1978 · 25 min

Grendel plans two weddings and a funeral to cement his hold over Tara. The Doctor and K-9 race to foil him and save the Time Lady's life.

S16·E17 Core

The Power of Kroll (1)

Dec 23, 1978 · 25 min

The Third Moon of Delta Magna, The Future. The Doctor and Romana arrive in search of the fifth segment and are immediately swept up in a conflict between the crew of a new refinery

S16·E18 Core

The Power of Kroll (2)

Dec 30, 1978 · 25 min

The Doctor and Romana try to avoid being sacrificed to Kroll – just in time for the real monster to appear.

S16·E19 Core

The Power of Kroll (3)

Jan 6, 1979 · 25 min

The massive Kroll is awake and killing anyone in its path. And the swampies are determined to appease it – by sacrificing the Doctor and Romana.

S16·E20 Core

The Power of Kroll (4)

Jan 13, 1979 · 25 min

The Doctor and Romana are trapped between the monstrous Kroll and the insane refinery commander. And there is no sign of the fifth segment of the Key to Time.

S16·E21 Core

The Armageddon Factor (1)

Jan 20, 1979 · 25 min

Searching for the sixth segment, the Doctor and Romana land in the midst of a brutal nuclear war between the planets Atrios and Zeos.

S16·E22 Core

The Armageddon Factor (2)

Jan 27, 1979 · 25 min

Swept up in an apocalyptic war, the Doctor must help the Marshal defend his planet. But who or what controls the Marshal?

S16·E23 Core

The Armageddon Factor (3)

Feb 3, 1979 · 25 min

The Doctor meets a new enemy – the Shadow – who wants the Key to Time. And the Atrian-Zeon war is approaching an awful climax.

S16·E24 Core

The Armageddon Factor (4)

Feb 10, 1979 · 25 min

The Doctor is forced into a desperate gambit to prevent a massacre. But it is getting harder to tell friend from foe.

S16·E25 Mytharc

The Armageddon Factor (5)

Feb 17, 1979 · 25 min

The Doctor and Romana finally venture into the Shadow's lair. The Shadow appears to hold all the cards but the Doctor has found an old friend.

S16·E26 Mytharc

The Armageddon Factor (6)

Feb 24, 1979 · 25 min

The Doctor and the Shadow have their final confrontation to take control of the Key to Time. Completing it may entail an awful sacrifice. And the Black Guardian will do anything to

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