Jayce, suspicious of a trap, is nevertheless lured to a radiation hot planet by Dr. Zorg, a bitter rival of Audric's. Flora and Herc stay behind as backup, but their vehicles are damaged by an enormous mutation and they are exposed to radiation and rendered useless to Jayce where he, Gillian and Oon are indeed trapped.
Saw Boss enlists the aid of the Life Eater to be rid of Jayce, but the job must be done by the Life Eater's conditions: he causes his subjects to face their worst fears and if they weaken even for a moment, give in to their fears, and betray their friends, their life force is trapped forever by the Life Eater.
The Lightning League try to stop Saw Boss from taking control of the Edro Lifeship, a vessel which has been transporting the Edro civilisation towards a new home for 5000 years. The Edro defence system, Myrmidon, seems oblivious of the Monster Minds presence and refuses to let Jayce speak to the Edro and warn them of the danger they face.
Saw Boss learns the Vine Stopper, a weapon created by Audric, could be reversed to speed up the vines' growth and sends troops to capture it. When the Lightning League hear of Saw Boss' plans they race to where Audric has hidden the device to secure it before the Monster Minds can but accidentally trigger a self destruct sequence that threatens to destroy the device and the whole planet.
While investigating convoys of slaves and equipment heading for the Black Nebula, the Lightning League hear rumours that the Monster Minds are building Doom Flower, a space station that will carry them to another universe with more suns and nutrients, allowing them to grow powerful and return unstoppable.
The planet Baz sprays all their plants with pesticide to keep the Monster Minds from invading their planet, but the Monster Minds send vines to cut them off from outside shipments of food. Zena, the princess of the planet, contacts Jayce for help, but when the Lightning League arrives on Baz the pesticides begin to kill Flora, and the Monster Minds prevent them from taking her to safety.
The Monster Minds set a trap for Jayce, offering him Audric in exchange for the root. Audric proves to be just an illusion generated by King Phineas after Saw Boss threatened to destroy his planet. The Lightning League and King Phineas must work together to fight the Monster Minds and save his people.
The Lightning League discover the Monster Minds about to take over a planet where all plantlife grows to many times its original size. Fearing an army of gigantic Monster Mind drones, they go in search for allies to help the fight, but find the native order of knights very hostile to all foreigners.
When one of Audric's experiments goes wrong, Saw Boss and the Monster Minds are created and set out to conquer the galaxy. Audric creates a magic root which can fight the Monster Minds but it is split into two, one half is taken by Audric, the other by his son, Jayce. The Lightning League seek the help of Herc Stormsailor to escape the planet and locate Audric.