At Coal Hill School, teachers Ian Chesterton and Barbara Wright have concerns about pupil Susan Foreman, who has an alien outlook on England. When the teachers visit her address to investigate, they encounter a police box and hear Susan's voice inside. An old man arrives, but refuses to let the teachers inside the police box. They force their way inside to find Susan in a futuristic control room that is larger than the police box exterior. Susan explains that the object is a time and space machine called the TARDIS and the old man is her grandfather.