If you could touch the alien sand, and hear the cry of strange birds, and watch them wheel in another sky, would that satisfy you?We commence with the World's Trippiest Title Sequence and the first time an audience would hear the "Oooh-ee-oooh" of the theme tune. note Two teachers, Barbara Wright and Ian Chesterton, think their super-bright pupil, Susan Foreman (a brown-eyed girl, complete with transistor radio), is a bit on the strange side. She's bored with regular physics and math and wants to move on to multidimensional physics and maths, and she thinks that the UK has decimalised its currency (which hasn't yet happened in 1963)note . So, they decide to follow her home one night. This being 1963, it's benign concern for the welfare of a child, and not at all creepy.They arrive at Susan's home address of 76 Totter's Lane. It's a junkyard. They hear Susan's voice coming from inside a police box. Thinking that her grandfather, "I. M. Foreman", has locked her in there, they proceed to open the door and enter the TARDIS. Which is bigger on the inside than out. Her grandfather, a crotchety old man, is the Doctor.Deciding that he can't have them tell the world about the Cool Ship and that the "Foremans" will need to leave the 1960's again, he starts up the TARDIS, acquiring the first two companions via abduction. Ian and Barbara are knocked unconscious by the time travel.When they've landed again, the foursome step out of the TARDIS and Susan quickly exposits that it was supposed to have changed shape: the first clue that it's somewhat less than reliable. Before long, the Doctor is kidnapped by a tribe of cavemen when they see him smoking his pipe which he never smokes again. This tribe has lost the ability to make fire, and the Doctor agrees to placate them by giving them fire, but unfortunately he has lost his matches. His three companions try to rescue him, but only succeed in getting themselves captured too. In the middle of all that, the Doctor decides to simply kill a friendly but wounded cavemen who's slowing them down a bit. This earns him his first ever What the Hell, Hero? from Ian, who prevents the murder. The tribe of primitive humans with monolithic names keep their captives in a cave full of skulls, skulls that have been obviously split open. Charming.A friendly (well, less hostile) tribesperson unties them, and they make tracks. Eventually, the Doctor tricks the hostile aspiring caveman leader into admitting he's a murderer, Ian gives the less hostile aspiring caveman leader the gift of fire, and they all escape back to the TARDIS. But since they had to take off in a hurry on account to avoid being speared, the Doctor was unable to make the calculations necessary to chart a course back to 1963. Hopefully their next landing spot will be a bit less eventful...NB: This story is commonly also called "100,000 BC", and less commonly called "The Tribe of Gum". "An Unearthly Child" is the title of the first episode (episodes were individually named until season 3) and is applied to the entire first serial through synecdoche.
— Part Two - "The Cave of Skulls"