The hunt for the fifth segment of the Key to Time lands the Doctor and Romana in trouble on the third moon of Delta Magna.
A revolutionary new textile formula gets stolen and the developer's daughter asks Simon for help.
Oscar Newley has perfected a new fuel injection system for his racing car and approaches Simon for financial backing.
Emma is behind the wheel for a deadly car race.
Agents in Steed's department are being fooled into giving away secrets, by men posing as Army officers at a fake Government training establishment. And their next victim is... Tara King.