Finding a Dalek

Wounded, after being shot by The Master, it is up to Jo Grant to help The Doctor into the TARDIS. Before collapsing he sends a message to the Time Lords via its telepathic circuits. Jo then helps him to a couch where he falls into a deep coma. Shortly afterwards the TARDIS arrives on the planet Spiridon and Jo decides to go outside to find help. As she leaves the TARDIS, which has landed in a jungle, a plant sprays her with a liquid. On exploring her surroundings she finds some footprints and decides to follow them. They lead her to a crashed spaceship in which she discovers a dead pilot. She is found there by two Thals, Taron and Vaber. After explaining that she requires assistance with The Doctor a third Thal, Codal, calls the others away as someone, or something, is approaching. Jo hides in a cupboard as an invisible creature enters the craft and starts searching.

Back in the TARDIS The Doctor recovers to find Jo is missing. He also realises that there is no oxygen and the doors refuse to open. He is saved from suffocation by the Thals who remove a fungus growth covering the outside of the TARDIS and help The Doctor out. When one of the plants sprays The Doctor Taron uses another spray to kill the fungus that is starting to grow on him. He warns The Doctor that if left untreated, it would quickly cover his whole body and kill him. They then make their way back to their spaceship so as to find Jo but instead they encounter an invisible Dalek.

Jo, who has by now discovered that she has the fungus growth on her hand, is found and taken by an invisible Spiridon. But Codal is captured by a group of other Spiridons. The Doctor and the two Thals arrive just as two Daleks approach to destroy the Thal’s spaceship. Thinking that Jo is still inside The Doctor is captured when he tries to stop them.

Jo and a Thal

Jo, however, is being treated by a Spiridon called Wester, who she learns is against the Daleks. Jo soon recovers and decides to enter the Dalek city so as to rescue The Doctor. Meanwhile Vaber wants to blow up the Dalek city but Taron advocates caution. Another spaceship from Skaro arrives but it crashes. The only survivors are an old love of Taron's, Rebec. She is accompanied by Latep and Marat. They have come to warn Taron that somewhere on the planet is an army of ten thousand Daleks…

In the Dalek city, The Doctor has been placed in a cell with Codal. They manage to escape and find themselves in the lower levels of the city just as Taron, Rebec and Marat require help getting out of a ventilation shaft. They have gained entry to the Dalek’s city via a network of icy passages. They explain to The Doctor that the Dalek’s city is built on an ice volcano, where the ice although below freezing is still a liquid, and that while inside the tunnels an eruption had started. The three Thals manage to escape from the ventilation shaft just before the flow of ice reaches them and before the Daleks close the ducts to seal the city from the advancing ice.

Inside the Dalek's Base

Daleks then arrive and Marat is exterminated as he tries to hold them off. The Daleks however, find a map on his body showing the location of where the Thals have hidden their explosives and a patrol is ordered to locate and destroy them. Jo, who has managed to enter the Dalek’s city and is hiding in a control area, overhears the Daleks and knowing how important the explosives are to the Thals she follows the Dalek patrol. When the Daleks discover the explosives they set the timers to destroy them. However, when the Daleks have left the area Jo manages to disarm two of the three bombs. She carries them away and hides them elsewhere before heading back towards the entrance to the Dalek’s city.

Trapped in the lower levels The Doctor discovers a huge Dalek army in a large cave, frozen in suspended animation due to the icy cold temperature. Realising that they have discovered something very important The Doctor and the Thals have to find a way of escaping from the Dalek’s city. This they achieve by making a hot air balloon and allowing it to pull them up a ventilation shaft. When they reach the top they find themselves on the planet’s surface. A Dalek though is pursuing them up the shaft on an anti-gravitational disk so they push some rocks down the shaft which kills the Dalek.

The Doctor and the Thals meet up with Jo and they all decide to spend the night at the Plane of Stones, an area which retains the heat from the day. Overnight, Vaber leaves to try and destroy the Dalek’s city alone but he is caught by the Spiridons. Taron and Codal ambush the party as it returns to the Dalek’s city and are able to commandeer their purple fur cloaks which they can use as a disguise. Wester then arrives at the Plane of Stones and warns The Doctor and Jo that the Daleks are heading towards them. Vaber is exterminated by the Daleks but Taron and Codal manage to get the bombs, Jo had salvaged, and return to The Doctor. They disable two Daleks by pushing them into ice pools. They use one of the Daleks, with Rebec inside, and the commandeered purple fur cloaks, so that they look like a Dalek patrol which they plan will enable them to get into the Dalek’s city. To increase the chance of reaching the Dalek army, that The Doctor discovered earlier, Latep and Jo descend down the ventilation shaft. However, on their way to the top of the shaft Jo and Latep witness the arrival of the Dalek Supreme who has arrived to take charge of operations on the planet.

The Dalek Supreme

The Doctor, Jo and the Thals though are unaware that the Daleks are preparing a bacteria which will destroy all life on Spiridon. Only the Daleks and their slave workers will be given immunity. Wester, on learning what the Daleks are planning, releases the bacteria early, trapping the immune Daleks in the isolation room forever and killing himself instantly.

In the Dalek city, The Doctor's party is discovered but they still manage to make their way to the lower levels, abandoning the Dalek casing along the way. They are all reunited at the bottom of the ventilation shaft. The Doctor initially plans to lock the refrigeration unit on, but the Dalek Supreme orders the Dalek army revived and the unit is switched off. Instead, while the others escape back up the ventilation shaft, The Doctor uses Codal's bomb which opens a fissure in the cave wall. This sets off the ice volcano which destroys the approaching Daleks and buries the whole Dalek army in ice.

With the Dalek’s plans in ruins The Doctor and Jo watch the Thals depart in the Dalek Supreme's ship before returning to the TARDIS.