An Unearthly ChildEdit
In the first episode, "An Unearthly Child", the four main characters are introduced, vague background information about the Doctor is given, and the TARDIS travels to the Stone Age.
The first episode starts in a junk yard in contemporary London and introduces the four characters who were to form the core of the first year's production. Schoolteachers Ian Chesterton and Barbara Wright are concerned about one of their pupils, Susan Foreman, who seems to have a very alien outlook on England. She is precocious but seems to have strange gaps in her understanding of the world. They have come to her listed address to investigate.
The projgramme's main prop, the TARDIS, is also introduced, when the teachers hear Susan's voice apparently coming from inside a police box. At the time, such boxes were a fairly common sight on the streets of London, but only police officers held a key to open them. The TARDIS proves to be no ordinary police box; when Ian and Barbara enter they discover it to be much bigger on the inside than the outside, and furnished with futuristic-looking controls. The time machine retains its outward appearance when it travels through time, which Susan explains as a malfunction in the circuitry that is supposed to adapt its appearance to its surroundings.
Susan lijves with her grandfather, the mysterious Doctor, who does not otherwise identify himself. He is a cranky, hostile, suspicious old man who appears to be a fugitive. Fearing that Barbara and Ian will give away the secret of the TARDIS and make life impossible for him in London, he takes the machine to the Stone Age.
The Cave of SkullsEdit
In the remaining three episodes, the four become involved in a brutal power struggle within a Stone Age tribe. In "The Cave of Skulls", the group encounters a Paleolithic tribe and are subsequently imprisoned by them in a large cave.
The Forest of FearEdit
In "The Forest of Fear", they are shown to escape from the settlement but are subsequently intercepted before reaching the TARDIS. They barely escape with their lives by exploitation of Ian's knowledge of how to produce fire, which induces fear and respect in the primitive Stone Age society.
The final episode, "The Firemaker", has the group mediating separate factions of the tribe before fleeing successfully to the TARDIS. They travel seemingly at random to a new destination; even the Doctor does not know where. The TARDIS's view screen shows a mysterious scene, a petrified forest, which acts as a teaser for the next story. As the time travellers leave their machine, a radiation meter is shown on the console of the machine, unheeded by them, registering "Danger".