Plot

Two schoolteachers investigate the personal life of one of their brilliant students and her mysterious grandfather.

Two schoolteachers, Ian Chesterton and Barbara Wright, become concerned by the unusual behavior of their fifteen-year-old student, Susan Foreman. When they follow her home, they meet her mysterious grandfather, the Doctor, and find themselves unwilling passengers on his time ship, the TARDIS...s—Sarah Hadley

London, 1963. A lone constable walks down a foggy street, checking locks and making sure all is well. He passes the junk yard of I.M. Foreman without a second glance. Little does he know that behind the gate of the junk yard sits a blue Police Call Box, one that hums with a mysterious power.

The next day at Coal Hill School, history teacher Barbara Wright enters the lab classroom of science teacher Ian Chesterton. She expresses concern about one of her students, Susan Foreman. Ian admits he is puzzled by her as well. She seems to know more about science than he does. Barbara tells him that Susan's homework has been below par in her class, but when she offered to tutor Susan at home the girl insisted her grandfather wouldn't allow it. Concerned, Barbara got Susan's home address from the office secretary, only to discover it was a junk yard. Ian agrees to accompany Barbra to the address to check it out. Barbara brings Ian into her classroom where Susan is waiting to borrow a book on the French Revolution. Barbara gives her the book and the two teachers leave. Susan looks through the book, muttering about how the facts in it are all wrong.

As Barbara and Ian sit in a car across the street from the junk yard, they talk about some of Susan's oddities: she doesn't understand English money, she can't work problems in only three dimensions without adding the dimensions of time and space. They see Susan enter the junk yard and go in after her, but there is no sign of her in there. They discover the Police Call Box, and Ian notices it's vibrating almost like it's alive. They hear a sound and hide as an old man (The Doctor) enters the junk yard. He is about to unlock the box when Susan calls out from inside. Ian and Barbara confront The Doctor, demanding to know why Susan is inside the box. He denies everything and insists they go for the police if they want to look foolish. Just as they are about to leave the door to the box opens and they hear Susan's voice again. Before The Doctor can stop them they rush inside.

The teachers find themselves in what looks like a control room of a spaceship. The room is enormous, with bits of furniture about, but the center of the room is dominated by a large hexagonal control panel with what looks like a tube of enormous crystals rising up from the center. Ian can't understand how the room can be larger than the box they entered. The Doctor and Susan explain that they are from another time and another planet, exiles roaming through time and space in their ship called a TARDIS (an acronym for Time And Relative Dimensions In Space). Ian and Barbara try to convince Susan that the whole idea of time travel is make-believe, and The Doctor becomes infuriated. Susan begs him to let the teachers go, but he warns her if he does then he and Susan will have to leave twentieth century London. Susan tells him she would rather leave the ship, and while her back is turned The Doctor powers up the TARDIS. They move through time and space, and materialize in the middle of a bleak landscape. As the episode ends, we see the shadow of something approaching the ship.