Dr. Who had invented time travel in the form of Tardis, a space-time machine, the exterior of which looked like a police box. When Barbara's boyfriend Ian Chesterton was visiting his house, he, Susan and Barbara went to have a look at Tardis. Ian accidentally pulled a lever and the four of them were transported to Skaro, the home planet of the Daleks, where they helped the Thals battle the Daleks. Tardis subsequently materialised on Oldark Moor, where Dr. Who and his companions encountered Count Tarkin. (NOTVALID: The House on Oldark Moor)