Susan Foreman was the Doctor's granddaughter. After landing on Earth for repairs to the TARDIS, Susan enrolled at Coal Hill School in Shoreditch where her advanced knowledge of history and science attract the attention of schoolteachers Barbara and Ian. Attempting to solve the mystery of the "unearthly child," Ian and Barbara follow Susan back to the junkyard, where they hear her voice coming from what appears to be a police box. When they investigate further, they discover that the police box exterior hides the much larger interior of the TARDIS, and are whisked away on an adventure in time and space with the Doctor and Susan, against their will.
Susan continued to travel with the Doctor and her two teachers until the 1964 serial, The Dalek Invasion of Earth. During the events of that story, Susan falls in love with David Campbell, a young freedom fighter in the 22nd century. However, Susan feels that she has to stay with and take care of her grandfather. The Doctor, realizing that Susan is now a grown woman and deserves a future away from him, locks her out of the TARDIS and leaves after a tearful farewell.
Susan displayed less knowledge about the workings of the TARDIS than her grandfather and was even naive to dangers that existed on the planets they visited. Also while she showed knowledge beyond earth science she did not display the advanced knowledge that was seen in other people of Gallifrey. Although it has never been explicitly established whether she can regenerate (though it is usually assumed that she can), she does display telepathic ability on occasion.
