Doctor Who (1963–1989)
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The Sea of Death 

On the planet Marinus, the Doctor and his companions are enlisted by Arbitan to seek out the keys to an ancient and powerful machine. Their quest takes them across time and space; will they... See full summary »




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Episode cast overview:
Martin Cort ...
Peter Stenson ...
Gordon Wales ...


On the planet Marinus, the Doctor and his companions are enlisted by Arbitan to seek out the keys to an ancient and powerful machine. Their quest takes them across time and space; will they be able to return the keys before Marinus falls under the control of the alien Voord? (Originally broadcast in six parts.) Written by Sarah Hadley

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Release Date:

11 April 1964 (UK)  »

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Aspect Ratio:

1.33 : 1
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Did You Know?


Fans voted this number 126 in a countdown of the 163 Doctor Who (1963) stories in Outpost Gallifrey's 40th anniversary poll in 2003. See more »


After the Doctor goes into the pyramid, someone's leg appears on the lower right side of the screen just before the shot ends. See more »


Ian Chesterton: It's Barbara's travel dial. Look! There's blood on it!
See more »


Featured in Girls! Girls! Girls! The 1960s (2009) See more »

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User Reviews

Fast-Paced "Quest" story
22 December 2008 | by (Camden, NJ (The Forbidden Zone)) – See all my reviews

THE KEYS OF MARINUS, from the first time I saw it in the mid-80's, has been my favorite story from the 1st season of DOCTOR WHO. Terry Nation has shown he can be inspired (when he's not writing about killer trashcans) and I think he outdid himself here.

The Doctor & co. find themselves trapped on an island containing a machine that can affect the will-power and behavior of an entire planet, and are coerced into retrieving several electronic micro-"keys" designed to activate it, before a power-mad group known as The Voord can get their hands on it. And so, in quick succession, using "travel-dials" worn on the wrist (rather similar to ones supplied by The Time Lords in GENESIS OF THE DALEKS many years later), they find themselves in a city overcome by illusion-inducing aliens; a botanist working in a temple surrounded by menacing plant-life (shades of DAY OF THE TRIFIDS and the DW story SEEDS OF DOOM); a snowbound trapper with amorous intentions toward Barbara and a cave filled with frozen warriors who come to life (in a scene that reminds me of on in the much-later story WARRIOR'S GATE); and a murder mystery with Ian as the suspect, and The Doctor acting as defense attorney! The story structure is rather similar to "The Key To Time" (season 16), except instead of 6 connected stories, this one takes place over only 6 episodes! The more I watched the William Hartnell stories, the more I came to realize that many great ideas and innovations seen in later seasons all had their origins in his era. And, while many of the longer stories in the early years tended to be slow-moving, this one nearly leaves you gasping for breath.

Several familiar faces guest-star over the course of the serial, including George Colouris (TARZAN AND THE LOST SAFARI, ARABESQUE), as Arbitan, the inventor of the behavior-modifying machine; Francis De Wolff (HOUND OF THE BASKERVILLES, FROM Russia WITH LOVE) as the brutal hermit; Robin Phillips (TALES FROM THE CRYPT) as Altos, who befriends the heroes as they help him in his quest; Donald Pickering (who returned for THE FACELESS ONES and much later, TIME AND THE RANI, but whom I most remember for a RETURN OF THE SAINT episode, "The Arrangement", as the misguided politician married to the mentally-unstable Sarah Douglas) as the prosecuting attorney with an ulterior motive; and Fiona Walker (I CLAUDIUS) as the devious wife of a security guard. Watching the story again recently, it slipped right by me that Walker had later returned in a much more prominent (and over-the-top) performance in the story SILVER NEMESIS!

Unlike many later seasons where characters got good introductory stories and then little good writing after, the characters during Verity Lambert's run as Producer (seasons 1-2) tended to grow and develop the longer the show went on. So it is, in KEYS I really got to like the entire regular cast, whose characters had all grown much more likable and closer together by this point. I also got a charge out of seeing The Doctor play defense attorney. I'm reminded that late in the run of DARK SHADOWS, during the "1840" sequence, Barnarbas Collins took a stab at the same situation, but to much lesser effect. (He LOST, and his client was only saved by outside circumstances.)

KEYS... may be the closest WHO ever got to the feel of the old FLASH GORDON serials.

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