Well, we’ve made it to the second season, so let’s get started with a serial whose premise also became a level in “Super Mario Bros. 3″…
As the TARDIS lands in what the Doctor assures Barbara and Ian is their native time, something malfunctions and the Doctor panics. When they try to view what’s outside, the scanner breaks. Outside they’re puzzled by what seems to be a stone monument shaped like a massive pebble. Splitting up to investigate further, Susan and Ian find a dead ant the size of a cat while the Doctor and Barbara find a gigantic earthworm that’s also dead. Soon Ian and Susan also find a large box of stock (that is, the broth kind, not the finance kind) that was manufactured in Norwich. Simultaneously the Doctor and Susan realize that the TARDIS and they as well have become smaller than an inch. Unfortunately, the revelation comes a bit too late for Ian, who happens to be standing on a giant matchbox that gets picked up. The man who inadvertently carried off Ian is a government scientist named Dr. Farrow, who is there to analyze a new insecticide, DN6, about to be released into the market by a company owned by Mr. Forrester. Farrow tells Forrester that he’s concluded that DN6 works too well, completely wiping out even beneficial insect life, and must advise the authorities not to allow the formula to be released. Desperately Forrester, whose company is on the verge of ruin, tries to bribe Farrow, but he insists, “This isn’t business, this is science.” Forrester shoots Farrow before he can call and make his report.
After seeing a bee drop dead, Barbara and the Doctor deduce that there is a poison around and that it endangers them as well. Escaping the matchbox, Ian is found by the others on the porch; unfortunately, Forrester’s cat finds them as well. They manage to cause the cat to lose interest by standing still, but worry if the creature will be back. The sounds of someone stomping into the room scatters the travelers and drives Barbara and Ian to hide in Farrow’s bag. Meanwhile DN6’s inventor, Smithers, who zealously believes that his invention will help end world hunger, agrees to help Forrester cover up the murder by trying to convince Farrow’s employers that he had already left for a planned vacation to France. Barbara and Ian end up on a table inside Smithers’ lab, which strands them. Barbara faints once she finds herself facing a giant fly, which soon dies after landing on a pile of seeds, coated with DN6, that Barbara had just touched.
The Doctor and Susan make it inside the lab too via a chemical sink. Barbara and Ian try make it down from the table to the sink, but are interrupted when Smithers, having just cleaned up Farrow’s blood, comes in to wash his hands, driving Susan and the Doctor back into the pipes. They manage to save themselves by standing in the overflow pipe. Back on the porch they find Farrow’s notepad with the DN6 formula written on it, which inspires them to use the information to stop the insecticide from being produced. The Doctor realizes that DN6 not only kills all insects, but has the potential to last within the soil and poison water and crops. Barbara, who has not told the others about being exposed to DN6, grows progressively weaker, which she blames on not eating. Going back into the house, the crew props up a phone, but find that the operator doesn’t hear them. The Doctor learns about Barbara’s condition and guesses that once she returns to normal size she will be well, but Barbara insists that they stay long enough to find a way to stop DN6.
Meanwhile the operator and her husband, a police officer, figure out, after Forrester tries to imitate Farrow to make a call to Farrow’s employers, that someone is imitating Farrow. Smithers finds Farrow’s notes and realizes what DN6 will do, but their argument is interrupted – and Forrester is knocked out – by an explosion in the lab deliberately caused by the Doctor and the others to attract attention. On the way back to the TARDIS, the Doctor sees the operator’s husband arrest Forrester and Smithers. After the Doctor repairs and malfunction and restores the TARDIS and everyone to their normal size, Barbara makes a full recovery.
First of all, it’s established that the TARDIS also has the capability to alter its size and those of everyone in it. While this seems like a silly, one-note idea, the concept becomes a plot point again later in the series, perhaps most notably in “Carnival of Monsters” and “The Armageddon Factor.”
Susan mentions that she and the Doctor were around for an “air raid.” Right away one might assume she’s referring to the Blitz, but, since from her description zeppelins were involved, it might be a reference that the Doctor was once right in the middle of World War I.
This serial also deserves to be remembered as the first time the Doctor and his companions hang around not because any of them are detained or because access to the TARDIS is blocked, but to do a good deed. It’s also the last serial to begin and end with the entire original cast.
As early as its second season opener, the showrunners were willing to break with the formula that was so rigidly sustained through the first season by having a setting that was neither an alien world (the exact opposite, in fact) or a historical era. It presages the madcap experimentalism that will dominate the show, for better or for worse, soon enough, and helps establish that “Doctor Who” is truly a series where just about anything could happen.
Beyond the novelty of the premise, this serial doesn’t really have much to offer. The serial’s production history bears that out, since it was decided to cut the serial from four episodes to three. It’s easy to see why; as creative as the show’s set designers had already proven themselves to be, the sets strain visibly at the budget limitations (especially in the Doctor and the companions’ “encounter” with a cat) and the fundamental idea of the Doctor and the others finding lethal obstacles and useful tools in mundane objects wears thin quickly. Further, while most of the first season serials had at least one aspect that expanded beyond the setting and the premise, like Barbara trying to alter history in “The Aztecs” or the Doctor and his companions navigating intrigue and rival political agendas in “The Reign of Terror”, “Planet of Giants” only has a half-hearted agricultural lesson on the downsides to too-powerful insecticides. This weakness might have been covered up if the writers had been willing to do more with the characters of Forrester and Smithers, but they hardly even begin to reach beyond the archetypes of the amoral capitalist and the mad scientist.
So all in all a weak opener to the second season, but I guess you could argue that the real opener is just around the corner…