As a pod of Moerani float through space, one of their youngsters hears a call and goes to investigate. It is unintentionally left behind.
The Doctor and Jamie arrive on Earth in the middle of a severe time storm. They make their way to the one relatively calm spot — Prague. All is not well in Prague, however, as they experience a time loop. Once Prague is caught up in the storm, the Earth will be destroyed.
Soon they are accosted by two armoured men and taken to the base of Kemen. He has captured a young Moerani and is using it to manipulate time and create a utopia on Earth. He wants the Doctor's help, but the Doctor refuses. To convince him, Kemen uses a weapon to age Jamie to a very old age, near death. The Doctor agrees to help.
As the Doctor is hooked up to Kemen's machine, he can sense the thoughts of the Moerani. It intends to kill itself, but first it helps the Doctor restore Earth to what it was. After it dies, the Doctor, with the remaining power of the Moerani, restores Jamie to his true age.
The pod of Moerani arrive to take the body of their missing youngster. Before they leave, they age Kemen to dust.
- Kemen's base is located in the tower of the Astronomical Clock.
- The Doctor calls Kemen a "temporal Einstein".
to be added