UNIT is tracking a UFO which seems to be threatening a nuclear reactor, so there is the usual debate about what to do. In a bit of a switch, the British government man, Chinn (Peter Bathurst), is quite rabid and wants to blow them to kingdom come immediately—at one point he puts all of UNIT under arrest--and the American, Agent Bill Filer (Paul Grist), is more rational and tends to side with the Doctor, who wants as usual to talk with them. Their argument is interrupted when the UFO disappears. The Axons land on Earth near the Nuton Power Complex. Filer goes out to study them and disappears as well. Their ship is mostly hidden underground, except for a mouth-like orifice in the ship that sends out tendrils to drag people inside for analysis. UNIT arrives to find Filer’s empty car and the sucked-dry body of a tramp. The Doctor and UNIT officers go inside, to find the interior alive with gooey strings like a pumpkin and Seventies psychedelia. Jo Grant is told to stay outside, but of course she doesn’t listen. Filer awakes in bondage and finds the Master hanging nearby.
The Axons appear—golden-haired, golden-skinned, and golden-eyed aliens, who say they are nearly out of fuel. They want to trade a miraculous substance called Axonite for an energy source. Axonite is an intelligent molecule than can replicate any other substance. The ship is in fact a single living organism called Axos, which drains energy through the Axonite and can feed on any life form. The Doctor is immediately suspicious, wondering why, if they have this powerful stuff, they have run out of fuel. What they really intend is to spread Axonite over all the Earth. Also, in the ship are a big eye on a stalk like the one in Jabba the Hutt’s palace, and a bunch of stringy root-ball aliens crossed with Monty Python’s Blancmange from Outer Space, that stumble around, scaring Jo. I once saw something like them when I left a sack of potatoes in the cellar for a couple months. The Axons discover that the Doctor is also a Time-Lord and reason that the Master is not so valuable as they thought. They duplicate Filer, but he escapes and ends up fighting himself.
The Master had been captured by Axos and offered Earth in exchange for his freedom. He escapes, his TARDIS having been seized by Axos, and makes his way to the Doctor’s TARDIS. It is unable to leave Earth because of the Doctor’s exile, but he thinks he can repair it. Axos becomes interested in time travel because of the Doctor, thinking they could travel in time as well as space and find more victims. Right now, they are becoming very dangerous. It appears Axonite will kill everyone and Earth will be sucked dry, unless the Doctor and the Master work together to destroy Axos. The Doctor confesses that he needs the Master because the Time-Lords have blocked his knowledge of dematerialization theory. The Doctor tricks Axos, offering to join with them against the Time-Lords, but he lets the Master repair his TARDIS and then traps Axos in a time loop. The Master gets his own TARDIS back and escapes, and the Doctor thinks he too is scot-free, but his TARDIS is programmed always to return to Earth. He is still in a time-lord decreed exile.
This story includes interior scenes of the TARDIS for the first time since the advent of the Third Doctor, and it is different from any TARDIS interior before or since. There are several strange or off-putting factors in the production. There was a sudden snowstorm in between filming the earlier and later scenes with the tramp, so dialog had to be written about the UFO causing weather anomalies. The Axos ship on the ground is clearly much smaller than the interior scenes reveal, so the explanation is that the huge ship buried itself in the ground. This is not the only time this has happened in a Doctor Who story, and we can be pretty sure that the budget was a factor. The Third Doctor could be as callous and egocentric as the First Doctor, but in this story he was particularly nasty; the scenes where he tricks the Master by offering to escape with him and let Earth go to hell seem a little too believable at times.