The Doctor tracks the missing scientists to Irongron's castle, where Linx is using them to repair his spaceship and construct advanced weapons for Irongron.
The Doctor and Sarah return to London in the present day only to find the city strangely deserted, while nearby UNIT are dealing with a series of monster appearances.
The Doctor and Sarah returns to present-day Earth, where they find London has been evacuated, and Dinosaurs are on the loose and they are mistaken for looters. Assisting U.N.I.T in the emergency, The Doctor and Sarah discovers corrupt politician Sir Charles Grover MP, renegade scientists Butler and Professor Whitaker and military officer General Finch are using a time machine to bring the dinosaurs from the past to the present as part of they scheme to bring the human race back to a "Golden Age" before the world was polluted.
The Doctor is rescued from Finch by the Brigadier and Benton and tries to persuade them to stop Grover before millions of people are erased from history.
As the TARDIS heads to the paradise planet Florana where the Doctor and Sarah go for a holiday, the TARDIS goes off-course and arrives on the barren planet Exxilon, where the TARDIS is loosing power. The Doctor and Sarah finds a group of humans and Daleks are searching for Parrinium, a mineral which is the only antidote to a space plague. Both parties encounter the native people and trouble ensues. In an attempt to find what caused the power-loss, the Doctor, chased by the Daleks, enter the Exxilon's lost city to be able to stop the power draining phenomenon.
Returning to the medieval planet Peladon (50 years after "The Curse of Peladon") The Doctor and Sarah find King Peladon's daughter Queen Thalira has inherited the throne and the galactic Federation is at war with Galaxy Five and The Federation requires the mineral Trisilicate that will end the war. Only to discover the miners led by the mad rebel Ettis are rebelling and refusing to work, as the ghost of the loyal best Aggedor is frightening and killing off Miners, only to discover the ghost of Aggedor is a holographic projection and the culprits are a task-force of ...
The Doctor turns the Aggedor spirit against the Ice Warriors to aid the Peladonians in their battle but Eckersley attacks him with the security system.
While the Doctor carries out an investigation into ESP, Mike Yates asks Sarah to look into some strange goings on at a meditation centre he's attending.
The Doctor and Sarah head to the meditation centre to try and get the crystal back while Lupton prepares to return it to Metebelis Three.But all their plans are disrupted when it is stolen by Tommy.