Episode Four (1st tx. 29/03/1975): On the war-torn planet Skaro, the Doctor is captured while attempting to prevent the Thals from firing a rocket at the city-dome of their enemies, the Kaleds. As the rocket impacts, the Doctor fears for the lives of his companions Harry and Sarah, who he had sent to the Kaled dome. Realising the threat of the experimental Kaled travel machines - the Daleks - still remains, the Doctor resumes his mission to prevent their development.
In a remote bunker, disfigured Kaled chief scientist Davros, whose treachery allowed the Thal rocketattack to succeed, plans his retaliation. At his command, three Daleks emerge and shoot his assistant Ronson, whom Davros falsely accuses of being a spy. Despite protests from the other scientists, Davros orders that the Dalek embryos be further genetically modified to eliminate any conscience or sense of pity, so that they may achieve his goal of absolute supremacy.
As the victorious Thals celebrate, their city is overrun by Daleks which exterminate everyone in sight. The Doctor and a Thal woman escape into the wasteland, where he urges her to assemble a fighting force from the survivors to stop Davros. Heading for Davros' bunker, he finds Harry and Sarah still alive. The Doctor reminds them that they must recover the Time Ring, as it provides their only link with the TARDIS, without which they can never leave Skaro.
In the bunker, Kaled scientists Gharman and Kavell secretly discuss their concerns about the Dalek project. They plan to give Davros an ultimatum - restore the creatures' sense of morality or they will destroy all his work. Nyder, a security chief loyal to Davros, infiltrates the resistance movement and obtains a list of conspirators' names from Gharman. With the dissidents exposed, Davros resolves that all the scientists will undergo surgery to remove their emotions.
The Doctor and his companions find their way into the Kaled bunker, only to be greeted by Davros and Nyder. They are restrained, and apparatus is attached to Harry and Sarah's heads, which Davros explains can create intense pain in their minds. Realising that the Doctor has defeated his Daleks in the future, Davros demands to know their weaknesses, so that he can correct their programming. The Doctor refuses. Increasing Harry and Sarah's pain setting, Davros screams that the Doctor can and will tell him.
