-> ''Why can't we go anywhere pleasant? Where there's no fighting, just peace and happiness?''
-->-- '''Victoria''' never did get it

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.

This story also sees the debut of the Sonic Screwdriver, the Doctor's signature gadget, which is used as a one-shot item to undo a release valve. It is also the only Second Doctor serial to not begin with "[[TheTheTitle The]]".

* BrownNote: Victoria's screaming defeats the weed creature.
* EverybodyLives
* EveryoneCallsHimBarkeep: 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".
* FreakOut: Robson
* HairpinLockpick: Used successfully by Victoria.
* ItsASmallWorldAfterAll: Lampshaded by Jamie.
* NotHimself: More and more people in the complex.
* MissingEpisode: Its the last ''Doctor Who'' serial from which all episodes are lost. The last three incomplete stories following this one are ''The Wheel in Space'' (episodes 3 and 6 of 6 exist, along with clips of episodes 1, 4, and 5), ''The Invasion'' (with 6 out of 8 episodes existing), and ''The Space Pirates'' (film inserts from episode 1 and all of episode 2 exist, of 6 total). Thankfully, ''Fury From the Deep'' does have a few existing censor clips and film trims, so we can at least get a glimpse of what this story would have looked like.
* PlantAliens: Maybe. It's never made clear whether the weed creatures are alien or not. They've been on Earth for centuries, wherever they originate.
* PuppeteerParasite
* ReasonableAuthorityFigure: Megan Jones, who gives the Doctor all the help she can once she is convinced of the truth of what he's saying.
* ScreamingWoman: The story puts this trope to constructive use.