to be added
Dr. Who and his granddaughters, Susan and Barbara, show Barbara's boyfriend Ian Who's latest and greatest experiment, a time machine called TARDIS. When Ian accidentally activates the machine, it takes them to a petrified jungle on a world devastated by an ancient nuclear war fought between the Daleks and the Thals. At the conclusion of the war, the Daleks, heavily mutated by radiation, encased themselves in protective machines and retreated into their city, while the humanoid Thals survived the fallout through the use of an anti-radiation drug and became a peaceful race of farmers. The Thals' crops have recently failed, however, and they have journeyed to the petrified jungle to seek help from their former enemies. The Daleks, meanwhile, although determined to become the dominant race on their world, are unable to leave the city due to their vulnerability to radiation and their reliance on static electricity to power their travel machines.
Ian is unnerved by the jungle and asks to return TARDIS but the Doctor, eager to investigate the city, fakes a leak in one of the vital Tardis fluid links to keep them out. The group decide to search the city for the mercury needed to refill the link but stumble across a case of Thal drug vials as they leave. In the city the Doctor, on reading a Geiger counter, realises that the planet is radioactive and in view of the fact that they are feeling unwell, deduces that they are developing radiation sickness. Suddenly, the Daleks appear and capture the travellers, confining them to a cell and seizing the Doctor's fluid link for inspection.
The Daleks know of the Thal drug and want to reproduce it in large quantities so that they can leave the city and exterminate the Thals. They offer to let the humans use some of the drug to cure their sickness if the vials left outside Tardis are brought to the city. Whilst carrying out the task Susan encounters Alydon, the Thal who left the vials. Alydon gives Susan a secondary drug supply to use in case the Daleks deviate from their promise and also lends her his plastic cape.
The Daleks discover Susan's secret drug supply, but allow the humans to treat themselves with it. They then summon Susan to write a letter to the Thals, informing them that they wish to end post-war hostilities and will leave food in their control room as an act of friendship. The adventurers discover that when the Thals arrive, however, they will be ambushed and exterminated.
When a Dalek comes to the cell to deliver food and water, the Doctor and his companions immobilise it by forcing it onto Susan's cape, thus insulating it from the charged metal floor. Ian takes the place of the creature inside the casing and notifies another Dalek that he is taking the Doctor, Barbara and Susan to the control room for questioning. Now free, the travellers shout a warning to the Thals who are entering the city and escape with them into the jungle, but not some of their number are killed by the Daleks.
Later the Daleks test the Thal drug on a number of themselves but find that it is deadly to them. With no way of leaving the city, they decide to detonate a neutron bomb to increase the radiation to a point at which not even the Thals can survive.
At the Thal camp, the Doctor urges Alydon to fight the Daleks to secure a safe future for his species. Alydon does not wish to enter another war, but the Doctor tells him that it is inevitable and inaction will only result in his people's extermination. When the Doctor notes that he needs to reclaim the fluid link from the Daleks so he and his companions can return home and offers his assistance, Alydon is convinced to fight for the freedom of his people as well as the Doctor's. Alydon, Susan and the Doctor lead the tribe to the front entrance of the city, where they attempt to confuse the enemy's scanners by reflecting light off small mirrors to give the impression of greater numbers. The plan fails when the Daleks appear and the Thals scatter, however, and Susan and the Doctor are captured.
Meanwhile, Ian and Barbara, guided by the Thals Ganatus, Antodus and Elyon, set out to infiltrate the city from the rear. While navigating a swamp, Elyon is killed by a marsh-dwelling mutation and the party is eventually forced to jump a chasm to proceed any further. Antodus falls short and plunges into the void, but manages to cling to the uneven rock face and is pulled up by the others.
In the city control room, the Daleks ignore the Doctor's appeals as they start the bomb countdown. Ian, Barbara, Ganatus and Antodus penetrate the city and join Alydon and the rest of the Thals, who have returned determined to rescue Susan and the Doctor. The Thals and humans enter the control room and struggle with the Daleks as the countdown drops closer to detonation. With seconds to go, Ian desperately tries to find "the right knob" to stop the countdown but is forced to dive for cover as the Daleks fire towards him in unison. In doing so, however, the aliens inadvertently destroy their own master control panel, disabling themselves as well as freezing the countdown.
Returning to Tardis in the jungle, the Doctor replaces the fluid link and announces that they are ready to return to their own time and place. Alydon bids farewell to the Doctor and his companions, leaving them a cloak to remember his people by. When the travellers depart in Tardis they materialise not back home, however, but in front of an irate caveman. As Dr. Who tries again, Susan ponders where they will end up next.
Deviations from televised story
to be added
to be added