The Lightning League travel to the disk planet Ellipsus, a D5X planet with two suns, where air holes connect the two sides. One side of Ellipsus is covered by a silicon desert where no plants can live and the native nomads actually consider plants to be dangerous leading them to believe Audric may have taken refuge there. Using the ship's scanner Gillian sees that Audric is on the planet and appears to be held captive. When they land Jayce tells Flora to stay behind and look after the Root while the others go after Audric.
Arriving at the village they see the people praying outside a large monument which contains the oracle. It instructs them to capture the Lightning League before Jayce uses the Root to infest their planet. When the Lightning League is discovered the nomads pursue them into the desert. In the ensuing battle Quick Draw refuses to obey Jayce's order to attack and they realise that it is because there is nothing to fight, the nomad pursuers are a mirage. Gillian realises that Audric too was a mirage designed to lure them there but they need the Root to be sure. They decide to head back to the barge.
Flora uses the ship's scanner to try and find the others but, when she sees an oasis, decides to go for a swim with Brock. The oasis turns out to be a mirage and Brock falls through an air hole to the other side of the planet. When Flora tries to return to the ship a nomad mirage has made it disappear.
Oon is driving Quick Draw and attempts to evade a mirage of a mountain causing him to crash and fall out of the vehicle and down an air hole. Flora arrives and tells them what happened. Jayce takes Armed Force and goes to find Brock and Oon. Meanwhile, Gillian attempts to use spare parts from the vehicles to make mirage resistant glasses and Herc makes repairs.
Oon and Brock find each other but are pursued by Monster Minds. Oon overhears their plan to invade the other side of the planet and capture Jayce but is captured by a Gun Trooper. Jayce arrives and rescues him. When Oon tells Jayce what he heard Jayce realises that the Monster Mind agent in the village must be posing as the oracle. They head back to the other side to expose the truth.
Using the anti-mirage glasses the Lightning League defeat another nomad attack. Jayce returns and sends the others to find the ship while he takes Drill Sergeant to the village. Jayce allows himself to be captured and taken to the monument then orders Drill Sergeant to attack. Drill Sergeant drills through the monument revealing the Saw Trooper inside. The nomads realise they have been tricked and agree to help Jayce.
Saw Boss orders a full scale invasion and an army of Snap Dragons pour through from the other side. The Lightning League are under attack when Jayce and the nomads arrive. The nomads use mirages to bolster their forces and together they defeat the Monster Minds, driving them back to the other side. Realising that he has lost, Saw Boss decides to flee the planet.