A dream of the Master and a glowing crystal leads the Doctor to the Newton Institute where his fellow Time Lord is conducting experiments with a machine he has named TOMTIT.
The TARDIS takes the Doctor and Jo to the Skybase station orbiting planet Solos – they have been sent by the Time Lords to deliver a sealed message to an unidentified person.
The Doctor and Jo visit the Master at maximum security prison on an island just off the coast of England where they are attacked by creatures related to the hibernating Silurians.
Taking a test flight in the TARDIS, the Doctor and Jo land on the storm lashed world of Peladon where the Doctor is mistaken for the chairman delegate from Earth.
The world is on the brink of war and Sir Reginald Styles is attempting to negotiate a settlement by arranging a peace conference to be held in his home, Auderly House.