The travellers arrive in the dangerous domain of the Toymaker, where their failure to win at a series of games could result in them becoming his playthings for eternity. Apparently innocuous nursery characters reveal deadly intent, and for companions Steven and Dodo the stakes are raised with every game of blind man's buff and musical chairs. The Doctor, meanwhile, is rendered invisible and given the challenge of completing the fiendishly difficult Trilogic game.

In their quest to gain control of the Solar System, the Daleks have taken posession of the Time Destructor, a weapon which threatens the safety of all who stand in their way. As they head up an alliance of alien races bent on destroying the human race, in their midst is none other than the treacherous Guardian of the Solar System, Mavic Chen.

Long, long ago on the great plains of Asia Minor, two mighty armies faced each other in mortal combat. The armies were the Greeks and the Trojans and the prize they were fighting for was Helen, the most beautiful woman in the world. To the Greeks it seemed the city of Troy was impregnable and only a miracle could bring them success. And then help comes to them in a most unexpected way as a strange blue box materializes close to their camp.

The TARDIS materialises at the Roof of the World, Central Asia, in 1289. There they meet Marco Polo and his fellow travellers on their mammoth journey across the Pamir Plateau and through the Gobi desert to Peking. Unfortunately for the Doctor, his Ship proves to be of immense interest to Polo, who sets his mind on presenting it to the mighty Kublai Khan on arrival at his court.

History must take its course...' The TARDIS materialises in the middle of a holy war between King Richard the Lionheart and the Saracen leader, Saladin, in 12th Century Palestine. As the Doctor, Vicki, Ian and Barbara explore their surroundings, they are suddenly caught up in a Saracen ambush - and Barbara is kidnapped. For the time travellers, intrigue and espionage ensue as they once again become involved in living history.