The one with a sonic screwdriver. Bet you that's not gonna show up again anytime soon.
The TARDIS lands on the surface of the sea and the travellers use a rubber dinghy to get ashore, where they are promptly shot by tranquiliser darts and taken prisoner.
They have arrived in a restricted area, a natural gas refinery, and there have been a series of problems in the pipes. One of the engineers insists that a rhythmic beating sound heard in the pipes must be a living creature.
It turns out that a creature of living weed has made its way into the pipes and can secrete either a gas or a foam that enables it to control the minds of anyone who comes into contact with it. It seems intent on establishing a colony based on the refinery.
The Doctor discovers that the weed is repelled by high-pitched noises when Victoria's screaming drives it away and he uses a recording of the screaming to defeat the weed creature.
Victoria, having had enough of the dangers of travelling with the Doctor, decides to stay with the family of one of the workers, Harris. Jamie is sad to see her go, but the Doctor understands.
"Fury from the Deep" is the only Second Doctor serial not begin with the word "the". It's also the debut of the Sonic Screwdriver, which would become the Doctor's signature do-anything gadget during the 1970s. Here, it's used to... unscrew some screws.
This was also the first serial to use 16mm film for location shooting, superseding prior 35mm equipment: as 16mm is a much smaller gauge than 35mm, the equipment for it was much smaller and thus more practical to use for extensive periods of time. 16mm would remain in use all the way until the last four seasons of the Classic Series, when the show went all-videotape due to professional camcorders becoming more practical for the BBC's use. That said, the Beeb didn't completely abandon 35mm after adopting 16mm equipment: it would still be utilized for occasional effects shots before the switch to fully-videotaped stories, and the 1996 TV movie, following American production standards, would be shot entirely on 35mm film (though it was edited on videotape due to the extensive use of CGI). Episode Two of "The Space Pirates" was also inexplicably shot entirely on 35mm, which led the BBC to preserve it for historical purposes.
"Fury" is the last serial to be missing in its entirety. An animated reconstruction was released in 2020, providing the viewer with two different options: a colour 16:9 presentation of all six episodes, and a black-and-white 4:3 presentation.
- Attack of the Killer Whatever: Killer seaweed. It's much scarier than it sounds.
- Bittersweet Ending: Good news, the weed creature was defeated and everybody that was possessed are alright. Bad news, Victoria decides to leave the TARDIS crew, leaving Jamie a bit down.
- Brown Note: Victoria's screaming defeats the weed creature.
- Call-Back: The Doctor is able to operate the helicopter in Episode 6, be remembering seeing Astrid Ferrier from "The Enemy of the World" operate it.
- Control Freak: Robson. He is obsessed with maintaining the outward appearance of his rigs working in perfect harmony, and by the midpoint he's reduced to screaming and frothing about how it's all his operation and nobody else's.
- Early Instalment Weirdness: The sonic screwdriver, which makes its debut here, is nothing more than a screwdriver that operates using concentrated sound waves. It wouldn't be until the Third Doctor's tenure that it would become the extreme Swiss army knife it's known as today.
- Everybody Lives: The Weed does not kill, it possesses. When it is destroyed, its victims recover.
- Everyone Calls Him "Barkeep": The Chief Engineer is one of the largest guest roles in the story. But he doesn't seem to have any name other than "Chief".
- Exactly What It Says on the Tin: The sonic screwdriver makes its first ever appearance in the series, and the Doctor uses it... to loosen a screw. For one of the few times ever in the series, the sonic screwdriver is actually used as a screwdriver rather than an all-purpose magic wand.
- Family-Unfriendly Violence: The surviving clip of Oak and Quill suddenly opening their mouths and eyes as wide as they can go and emitting toxic gas.
- Fat and Skinny: Mister Oak and Mister Quill. Oak is short and fat and cheerful, Quill is tall and skinny and lugubrious.
- Freak Out: Robson.
- Freeze-Frame Bonus: The animation adds the by-now obligatory calls forward, including the base's electronics being provided by International Electromatics (with the wonderfully sinister motto "Be like us! printed on them) and a Wanted poster for the Master.
- Hairpin Lockpick: Used successfully by Victoria.
- I Choose to Stay: Victoria stays with the Harris family.
- It's a Small World After All: Lampshaded by Jamie.
- Jerkass: Robson is a surly, unpleasant individual who prioritizes looking good and being in control over doing his job and his subordinates' welfare. He actually has to be browbeaten into letting the Doctor look over Harris's sick wife.
- Lampshade Hanging: Victoria mentions that the TARDIS always seems to land on Earth.
- Mean Boss: Robson. He refuses to take advice, knows it all and rails against his subordinates for the slightest perceived failure. That said, the Chief repeatedly stands up for him against van Lutyens, saying hes tough but dedicated, and worked his way up fair and square. Unfortunately, he genuinely loses his marbles over the course of the story.
- Next Sunday A.D.: The animated version adds calendars revealing the story takes place in 1975, which coincidentally sets it one year before the real-world airing of "The Seeds of Doom", which featured a similar base premise of malevolent vegetation.
- No Celebrities Were Harmed: Victor Pemberton based Oak and Quill on Laurel and Hardy, whom he had actually met in the past.
- Nothing Is Scarier:
- This story manages to make gas, foam and seaweed terrifying.
- An advantage of the episodes not surviving is that it works very well on audio.
- Not Himself: More and more people in the complex.
- Off-the-Shelf FX: A special prop was made for the sonic screwdriver, but due to the numbingly cold weather on location Patrick Troughton dropped and lost it. The whistle from Deborah Watling's lifejacket thus became the first ever sonic screwdriver.
- Opt Out: Victoria, tired of being traumatised all the time, chooses to stay with Harris and his family.
- Plant Aliens: Maybe. It's never made clear whether the weed creatures are alien or not, although mind-controlled Hodson's reference to the weeds' imminent takeover of "the human planet" at least hints at it. They've been on Earth for centuries, wherever they originate.
- Puppeteer Parasite: The weed can brainwash its victims and control them.
- Reasonable Authority Figure: Megan Jones, who gives the Doctor all the help she can once she is convinced of the truth of what he's saying.
- Screaming Woman: The story puts this trope to constructive use. The weed turns out to be weak to sound, and Victoria's screaming hits just the right pitch to act as a Brown Note.
- Those Two Bad Guys: Mister Oak and Mister Quill. Don't let them breathe on you.
- You Are in Command Now: After Robson is taken over by the weed monster, Harris assumes control of the rig.