A Lonely Orbit
Led by Quatre, the pilots (except Wu Fei) have sent their Gundams to the sun, to be destroyed. But in that time, Relena is kidnapped by the soldiers of Space Colony X18999, under the lead of Marimeia Kushrenada, daughter of Treize Kushrenada and Leia Barton; who declares independence of the colony and war to Earth. Her goal is to reach the same wish of his father. However the real mastermind is Dekim Barton, who wants to complete the Operation Meteor that was his own creation.
While Quatre goes on a mission to the Sun to recover the Gundams, Noin and Sally help Heero and Duo to infiltrate the colony to rescue Relena and stop Dekim's plot. However, they will find Wu Fei, who has joined forces with Marimeia's army, and Trowa, who is in his own mission to uncover Operation Meteor's true goal.
During the upcoming battles the five pilots will remember their past linkages to Dekim Barton and Operation Meteor, especially Trowa, who was in part responsible for the depart of Gundams to Earth in AC 195.
Heero and Duo will fail to take the colony and Trowa will retreat. Relena and Marimeia will discuss the goal of invading Earth again, after peace was reached with so much effort and sacrifice. When a misteryous man (Zechs) takes Tallgeese and plans to stop the invasion of Mobile Suits coming from space, Quatre manages to get back the Gundams and Trowa reveals Heero and Duo the truth behind Operation Meteor - a hecatomb to be raised by the drop of colony X18999 to Earth.
Trowa catches Dou for show as Heero escapes the colony to take the Gundam ZERO in outer space, allowing him to briefly land on Earth. As this happens, Zechs manages to terminate Dekim's space base, but he escapes and Zechs must watch the carriers landing on Earth...
Return to Eternity
Marimeia comes to Earth with Relena as her hostage. Only Lady Une has reached Marimeia's base in Bruselas meanwhile Zechs and Noin are trying to stop the army in Earth and the Gundam pilots, except Wu Fei, take their Gundams back and prepare to war. Duo, Trowa and Quatre came just in time to save Zechs and Noin, but even the five machines can't stop the huge army of Mobile Suits Dekim has prepared for them. Wu Fei is waiting for his opponent to come to Earth so he can reach justice. He fights Heero. Wu Fei feels he has failed to reach justice and he believes battlefields to be the place for people with him; however Heero believes war will only cause pain for humanity and for themselves.
After Wu Fei and Heero stop fighting, Heero leads to Bruselas, where he destroys Marimeia's palace. Wu Fei reaches the city also, being followed by people who don't want their peace to be broken. Marimeia gets shot by Dekim in her attempt to pretect Relena, and Dekim gets himself shot by his own operatives who had witnessed Dekim's real intentions.
After that the invasion is stopped and the five Gundams are destroyed, as the five Pilots leave the battlefields forever.