In 1963, a mysterious time traveler called "the Doctor" (William Hartnell), his granddaughter Susan (Carole Ann Ford) and two of her teachers, Ian (William Russell) and Barbara (Jacqueline Hill) were inadvertently transported to an alien world, thanks to the Doctor's time machine (the TARDIS) malfunctioning. There, they find a petrified forest and an empty city, where they discover that they've been exposed to dangerous amounts of radiation. But before they can return to the TARDIS to escape, they are captured by the city's inhabitants - robots with domed, bumped bodies, a single eye-stalk protruding from their head, and an energy weapon built into their frame. They are the Daleks, one group of survivors of a nuclear war that destroyed the planet. Driven underground and into their robotic tanks, the Daleks have become hostile towards anything that is not a Dalek - like, for example, the Doctor, Susan and her teachers.