It was a kind of portal - a portal into the myths of the ancient world . . . Everyone knows the Doctor loves museums (it's his way of keeping score). But when Jo Grant and the Doctor visit the British Museum in London, they might have got more than they bargained for. A mysterious object is revealed, which grants those who touch it strange visions of Greek Myths. Gods, warriors and monsters are contained within this device, which its discover calls the mythoscope. But there is something sinister at play. A powerful influence seems to be controlling the mythoscope . . . mastering it. Jo and the Doctor must enter the mythoscope to face an old and terrible enemy - bargaining with Zeus, battling dragons and journeying into the underworld. As dangers beset them on all sides, only an object of wondrous power can save them from total destruction . . .