This two-part "Doctor Who" serial introduces the shape-shifting character of Kamelion, an android sent to medieval England to pose as King John and help the evil Time Lord (known as "The Master") knock the real king off his throne. The Doctor senses something's afoot when he arrives in the TARDIS -- and in the middle of a jousting tournament, no less. But the plot thickens when he unmasks more than one impostor.