As the final battle between the White Fang colonist rebels and World Nation forces continues as things are monitored from the resource satellite MO-II by Lady Une and those loyal to the late Treize, Heero and Wing Zero continue their battle with Zechs/Millardo and the Epyon, while Trowa, Quatre, and Wufei do their best to provide support while Duo takes Doctor J and the other Gundam scientists to Peacemillion, still rammed into battleship Libra, to prevent White Fang's desperate bid to still carry out Operation Meteor with dropping the two ships on Earth. When Sally Po, Relena, and Howard arrive at MO-II with the surviving crew of Peacemillion, Une offers Relena a gun to finally take revenge for the murder of Vice Foreign Minister Darlian by Une some time ago, but Relena refuses, having had a change of heart thanks to her pacifist ideologies, and convinces Une to seek peace through means that don't involve more bloodshed.
Meanwhile, when one of Une's techs tells Howard they've evacuated the area where Libra and Peacemillion are to crash into Earth, Howard reveals that if both ships crash onto Earth, it will render the planet uninhabitable due to the nuclear winter that will be created by the ships. Shortly thereafter, Une makes contact with Noin, who is still watching the conflict between Wing Zero and Epyon, and has her broadcast it across Earth and the colonies, convincing both sides to seek peace.
Meanwhile, Duo drops off the Gundam scientists on Peacemillion, but as they prepare to activate the engines to counter those on Libra and push both ships off into deep space, they are confronted by Quinze, who refuses to let them interfere with Operation Meteor again, but despite threatening to shoot them if they do, Professor G activates the engines, and the resulting explosion as the engines activate kill Quinze, Doctor J, Professor G, Doktor S, Master O, and Instructor H. With the engines activated and at full power, Peacemillion is able to counter the forward momentum from the engines on Libra and force both ships away from Earth and into deep space. Unfortunately, Libra refuses to give up so easily, and manages to sever one section of itself to plummet back towards Earth. At the same time, the colony leaders announce that the White Fang are no longer a part of the colonies, renouncing them and asking for peace with the World Nation. Heero manages to defeat Zechs and the Epyon, then moves to assist in stopping the Libra block from falling to Earth. At the same time, Duo, Quatre, Trowa, and Wufei attempt to help as well, with Quatre and Sandrock Kai being assisted by the Maguanac Corps, who have come to help Master Quatre. Heero soon reaches the block's power core, but with Wing Zero's beam saber out of energy and its Vulcan cannons also empty of ammunition, Heero realizes the only option left is Wing Zero's self-destruct system.
As Relena, Sally, Une, Howard, and the others watch from MO-II, Heero prepares to activate the detonator, but Zechs appears in Epyon, and before Heero can stop him, Zechs has Epyon plunge its own energy sword into the power core, setting it to go critical. Heero tries to stop him, but Zechs tells Heero they will meet again before Epyon is engulfed in the resulting explosion. Despite Zechs detonating the power core, a large chunk of the block still heads for Earth. Une orders the Gundams to pull back, but as Heero and Wing Zero emerge from the rubble, with Wing Zero apparently having suffered damage to its shoulder, Heero asks Wing Zero to aid him in his mission, and the ZERO System complies, allowing Heero to see when Wufei busts through the wall ahead with Altron to return Wing Zero its Twin Buster Rifle. Affixing it back with Wing Zero's shield, Heero declares "Mission Accepted", before Wufei passes the message to the other Gundam pilots. Hearing Heero has Wing Zero's Twin Buster Rifle again, the Maguanacs cheer before they and Quatre pull out, Trowa following after emptying the last of Heavyarms' ammo, and Duo and Wufei right behind in Deathscythe Hell and Altron.
On MO-II, everyone watches as Heero flies Wing Zero ahead of the block to destroy it as it begins atmospheric reentry, and while some like Sally and Une express concern, Relena maintains the utmost faith that Heero will succeed. Once far enough ahead of the block, even as Wing Zero suffers additional damage from the friction of atmospheric reentry, Heero struggles to attain target lock on the block. Declaring that he will survive this mission, Heero finally stabilizes his aim, acquires target lock, and fires. It's a direct hit as the impact of Wing Zero's Twin Buster Rifle blast sets off secondary explosions across the hull of the severed block, soon leading to the entire block disintegrating in a bright, fiery explosion.
As the glare subsides and everyone stares at the glow left behind by the blast, one of Une's men screams "WE DID IT!" as the rest cheer in celebration as another announces that the remains of the block have burnt up. Among the celebrations, Relena's only concern is for Heero. Back with the Maguanacs and Gundams, Duo soon spots Wing Zero, back in its flight conversion, emerging unharmed from the glare, meaning Heero survived, as the Gundam Wing theme song plays.
- Duo: You've done it, Heero!
Wufei: Yeah! Naturally!
Trowa: Huh, he is quite the guy.
Quatre: Now I get it...It's Heero who is the heart of outer space.
(beat)
Heero: Mission...complete...Narrator: The year is After Colony 195. On this day, the formation of the new Earth Sphere United Nation, is passed at a conference between Earth and the Colonies.
Some time later, Noin arrives at a cemetery where Dorothy is paying her respects at presumably her grandfather Duke Dermail's gravestone, if not Treize's, to leave flowers at it. When Dorothy inquires as to why Noin doesn't leave anything at Zechs' gravestone, Noin tells her that she believes that Zechs is still alive somewhere in space and she'll see him again.
At one of the colonies, Relena, now following in her late foster father's footsteps as Vice Foreign Minister under her Darlian surname, is met by one of the colony representatives, who is disappointed that Relena is heading back to Earth to deal with her terraformation project when they were going to celebrate her birthday on the colony with her. At the shuttle bay, as Relena goes to her seat on the shuttle, a mechanic scoots by her, pardoning his rudeness, but when Relena gets to her seat, she finds a teddy bear and a card there. Going to the window, she spots the mechanic, and calls out to him, revealing the mechanic is Heero in disguise, having left the gifts for her. As he turns to look back up at her, she takes the card, and in an Ironic Echo to when she gave him his invite to her birthday party previously, tears it in half, before telling him to hand it to her in person next time. With a smile, Heero departs, and Relena looks after him with a warm smile.
Tropes:
- Book Ends: In the first episode, Heero tore up a birthday party invitation from Relena. At the end of this episode, Relena tears up some sort of note from Heero, saying he should deliver it personally next time.
- 11th-Hour Superpower: When Wing Zero gets its Twin Buster Rifle, giving Heero the firepower to destroy Libra and prevent the Colony Drop.
- Never Found the Body: Zechs is presumed dead. Naturally, he would appear in Endless Waltz.
