Because of the cancellation of the programme, the third and final series was never filmed: however, it advanced far into pre-production and scripts for it were written. TV Zone 22 carried a rough plot summary by Justin Richards and though his source is unclear, he seems to have seen BBC documents. The background article contains no direct quotations, which is a slight caution, but here it is, slightly tidied up. The story resumes with the refuge at the White Mountains camp in burning ruins: Julius and the others have, however, survived. (In the book, it is briefly explained that Julius had moved camp without telling the athletes sent into the City, in case of their minds being read.)

Will relates his discoveries about the City to Julius, but as plans are being formed the Tripods return to attack again, inflicting heavy casualties.

Will and Henry become separated from the free men and set off on a journey across Europe back to England, recruiting followers as they go. On the way they witness the Hunt of a human by Tripods, apparently for sport. Eventually they return to Wherton (their home village), and on Capping Day, where they are once again found by Ozymandias. He takes them to Julius's new headquarters, a castle on a clifftop on an island, where they are reunited with Fritz.

The rebels capture a Tripod, and the Master within it, using a green-painted man on a green-painted horse as bait. They carry out tests on the creature and refine their plans, but it is becoming apparent that there is a traitor in their midst. A band of armed men attack the castle, and when one of them is captured, he turns out to be one of Julius's own men. But even after this Julius's plans still seem to go wrong, and Will and Henry begin to suspect there is another traitor.

The free men prepare coordinated attacks on all three Cities, joined by an American girl and a Chinese delegation who will be responsible for attacking the second and third Tripod Cities (on the Panama canal and near Peking). In the European City, they succeed in remaining concealed while preparing the alcohol needed to poison the Masters: they capture the City but find themselves trapped within it.

They eventually escape, as the City is destroyed: having succeeded in rescuing Eloise, Will takes her home to the Chateau Ricordeau. But celebrations are curtailed by news that the American City has withstood attack.

Will, Henry, Fritz and Beanpole put forward their own plan but are over-ruled by Julius. Instead, they go hot-air ballooning, unaware that Beanpole sees the balloon as a potential way of bombing the last City. When the second raid fails, too, Julius has little choice but to adopt Beanpole's plan.

In the attack, Henry is killed. But the human race is released from the domination of the Tripods and the effects of the Cap.

William Golding once said he thought The Lord of the Flies was a good book because "something happens in every chapter", and the same could be said of The Pool of Fire: the version above crams even more in, the sub-plot of "traitors in our midst" being entirely new.

The major alteration is that Will and Fritz's journey overland to Egypt has been replaced by Will and Henry heading home across Europe, thus giving Henry a little more of the action, and of course Europe is easier to film in than the Middle East. (The production team intended to use Spain, and scouted a reservoir there to serve as the Panama Canal.) It's noteworthy that Eloise is restored to life, in Rowe's version, whereas in the books she had died the moment she had been taken into the City. But Henry still dies. How much of the book's post-war coda would have appeared is impossible to say, but it's clear that the BBC version was not going to glue a falsely happy ending onto Christopher's trilogy.

The most intriguing point, perhaps, is that the third season would have been so much of a "book-end" to the first, with Ozymandias, Eloise, the Ricordeaus and two of the major locations all making an unexpected reappearance. The episode in which Ozymandias discovers Will and Henry in Wherton, on Capping Day, would have been an ironic reprise of the very first episode. (The book has an element of this, too: Will finds himself recruiting just as he had once been recruited.)

We shall never know how it would have worked out.