1963. Worried by an unusual pupil, Susan Foreman, two of her teachers, Ian and Barbara, decide to follow her to her home in order to talk to her grandfather. Instead they see her enter a junkyard. When they follow her inside there is no sign, Although there is a strange, vibrating police telephone box. They hear Susan inside, and when her grandfather returns they barge past him and into the police box - where they find a large, brightly lit, room with a mushroom shaped console in the centre. The Doctor is not happy at the intrusion, and says that if he lets them go free they will inevitably tell someone about what they saw. Before anyone can stop him the Doctor dematerialises the TARDIS..
More than 40 years later, Doctor Who is still going strong with the eleventh incarnation of the Doctor, played by Matt Smith.
See also the following spin-off series which include many cross-over stories with Doctor Who: