Luna tells the scouts they need to journey to the moon to find out the truth of their past lives. To do so, they must wait until the next full moon. As the time passes, Bunny is happier because she knows she'll be able to do more when she knows the truth. Her father has the Silver Imperium Crystal made into a pendant that she can wear around her neck. As the time of the full moon approaches, Bunny's father can notice a change in her, like she's more grown up.

The night arrives, and Luna leads the scouts to the park. Bunny remembers it as the spot she was supposed to give Darien his pocket-watch back. They spent so much time arguing with each other, but even then Bunny was drawn to him. The scouts gather in the middle of park under the power of the white light of the full moon, sitting in the middle of the cloudless night sky.

Luna speaks a code and a circle appears in the middle of the park. The scouts gather inside it and join hands as they morph. A bright light shoots up, and suddenly the transformed scouts and Luna are floating in a bubble of light in space. They approach the moon and Luna tells to them to travel to Mare Serenitatis, the "Sea of Serenity".

They arrive on the moon, viewing the darkness around and see some blue-white ruins which they head towards. The ruins were where the Moon Castle once stood. Luna points out what used to be the Prayer Room, and the pillar of prayer, the Crystal Tower. In front of that a sword handle was coming out of the ground. Luna tells Mars, Mercury, Venus and Jupiter to pull it out. All four of them use all their strength to pull it out, exposing the stone sword.

An image appears before them, telling the scouts what they hold is the legendary sword that protects the Princess. She is the former Queen of the Silver Millenium, Serenity, called Selene, goddess of the Moon on Earth. She notices Sailor Moon, calling her Serenity. Sailor Moon realizes this was her mother from her past life.

Serenity explains that she lost her body, but the subcomputer of Moon Castle contains her spirit, showing it in the form of a hologram. It was the Queen who awoke the cats and has been watching their progress.

Queen Serenity turns to Sailor Moon, asking if she remembers the lush green dome of their past kingdom. Back in the Silver Millenium, Princess Serenity longed for the real green of Earth and snuck down there often, meeting her love. Those born on the moon have long lifespans, their duty being to protect the Silver Imperium Crystal, and watch over the Earth, protecting it from evil.

That summer so long ago the sun was very active. That activity was the Evil One, stealing into the Earth and controlling it's people who attacked the moon. Only Prince Endymion protected the moon, but was killed by his own people. In her sorrow, Princess Serenity committed suicide. Queen Serenity finally managed to seal away the Evil One, but her kingdom was already ruined. The Earth Kingdom was also destroyed, and began anew. The battle happened in ancient times.

But now, the Evil One has been uncovered. In the past, the shock of losing her daughter made Queen Serenity unable to use a complete seal on the Evil. But, she cannot redo sealing the enemy, so it is now up to Sailor Moon to use the power of the Silver Imperium Crystal to seal away the Evil One for good. However, Venus points out that part of the Crystal went into Tuxedo Mask's body and it does not have it's light. Queen Serenity tells Sailor Moon this is because of her desire to help him that part of the Crystal entered his body. She goes on to say that the Crystal follows Sailor Moon's heart. "Be proud of the fact that you are a Princess." But as the Queen is about to tell Sailor Moon the real reason she was reborn on Earth, the power runs out, and she just has time to tell her Serenity to find happiness.

The scouts return to Earth, noticing the resonant sound in the air that was missing on the moon, the water, the wind. They are part of this planet now, caring and yearning for it.

In the Dark Kingdom, Kunzite looks at the rocks that are all that is left of his three fellow warriors. He goes into another room, finding his master, Prince Endymion. Queen Beryl walks by, stopping at a large door and speaking a code. Kunzite follows as she goes down into the ground, and sees an almost solidified Metallia. Queen Beryl reports about Tuxedo Mask. Metallia demands the Silver Imperium Crystal, which Beryl plans to retrive using the captured Tuxedo Mask, saying Kunzite will not last much longer.

Queen Beryl goes up to where Tuxedo Mask lays and Kunzite approaches her. He says the other warriers cannot be revived even with the Crystal, since their bodies are destroyed. Then, he asks what she is doing with Prince Endymion. She tells him he gave his body to her, to always be reborn as one of her warriors. Beryl instructs him to go attack the humans, so that the Princess will come and he can take the Silver Imperium Crystal.

That night, an ice wave goes over the city, freezing the people in place and causing an emergency. In the control room, Luna tells the others of an unual heat source found in the Artic Circle that might be connected to the Dark Kingdom. Amy looks at another computer and notices what is going on in the city. All the scouts quickly morph and head out.

Sailor Moon and the scouts incounter Kunzite, who she recognizes as the one who carried off Tuxedo Mask. She uses "Moon Healing Escalation", melting the ice around all the people. Kunzite notices the Silver Imperium Crystal around Sailor Moon's neck. He catches her in a bubble of power and they both float high above the surface of the Earth, into space. She turns towards him and demands Tuxedo Mask. Kunzite offers to exchange the Crystal for the return of Tuxedo Mask, as a corpse. The Sailor Scouts follow Kunzite into space. All together, they unlease the "Sailor Planet Attack" which crumbles Kunzite. But, they still know nothing of Tuxedo Mask.

Back in the Dark Kingdom, Queen Beryl sarcatically laments Kunzite's demise. Using the power of Metallia, she awakens Tuxedo Mask as an agent of evil. He gets up, picking up the jewel of Kunzite, and sees all four stones in his hand. Beryl calls him Prince Endymion, her puppet. She instructs him to go to surface to kill the Princess and steal the Silver Imperium Crystal.