Act 40 - Dream 2, Mercury Dream

While Usagi and Chibiusa deal with their switched ages, Ami is attacked by Fish Eye. In an act of sheer willpower, Ami calls on her own Sailor Crystal, and her own talisman the Mercury Harp, and evolves into her Super Sailor form.

Plot
Mamoru wakes up in the hospital and is stunned to see Usagi and Chibiusa with their reversed ages. The Inner Senshi arrive and are also confused by it, and they discuss the new enemies. The doctor, who is Ami's mother, arrives and tells Mamoru that he has a strange shadow on his lungs, like an infection she has never seen before.

Mamoru goes home and takes Usagi with him. Meanwhile, Chibiusa returns to the Tsukino household, and has to use Luna P on Ikuko so the family does not realize what happened to the girls. Helios appears to Chibiusa and is surprised by her appearance, telling her that it must be the doing of the enemy. She asks if he knows of them, and about his true form, but he refuses to tell her, and merely says that he needs her help to break the seal of Golden Crystal.

At Mamoru's apartment, things are awkward between the two of them because of her childish form. Usagi is momentarily jealous of Chibiusa interfering with their relationship, but the two of them talk about how lonely she must be now that she can't get home. As Mamoru feels weakened by pain again, he tells Usagi that he sometimes feels like he's dragging her down, away from her dreams, but Usagi thinks that all she wants is to be with him forever.

Chibiusa sits on a swing at the park, and Diana observes that her parents would be proud of what a fine lady she has become, even if it is just a trick by the enemy. Even though her real self is still small, Chibiusa thinks about her dream to truly become a lady, and perhaps find her own prince someday.

Pegasus appears to Mamoru in a dream and apologizes for not being able to protect him and Elysion, and asks him to search for the Golden Crystal.

As Ami works on her computer late at night, she discovers the presence of a strange aura on the Azabu-Juuban shopping center which must be the work of the Dead Moon Circus. Her mother arrives home from work and is concerned that her daughter is working too hard, and says that she isn't being a good mother. Ami thinks about her father, a painter who she hasn't seen in years. She glances at a postcard that he sent her for her birthday, like he does every year.

In the circus tent, Queen Nehellenia's voice comes from a dark mirror, telling Zirconia that the forces of the White Moon are present on the Earth now and must be stopped. Zirconia finds the Amazoness Quartet and tells them to destroy their sworn enemies, the people of the White Moon. Fisheye volunteers to do it, and after searching, finds Ami, who he says carries a beautiful dream.

Ami speaks to Usagi on the phone, and discovers that she still hasn't changed back. After hanging up she goes out and walks through the rain, and passes a new fish store. She goes inside and finds tanks full of tropical fish, and the disguised PallaPalla sells her one that looks like one on the last postcard her father sent her.

At home, Ami falls asleep while watching her new fish in its tank. She wakes up and sees illusions of her mother shunning her and her father saying that he left because of her, then sees Usagi, Chibiusa, and Mamoru together and talking about how they don't need anyone else. Fish-Eye appears to her and tempts her with her dreams of being loved. She suddenly realizes it is an illusion and is attacked by Lemures. Ami tries to call for help, but falls under Fish-Eye's nightmare spell and begins to despair.

She hears Guardian Mercury calling to her and opens her eyes. The Guardian reminds her of her true dream, to protect everyone, and the Mercury Crystal appears, giving her a new transformation and attack. Using her new Mercury Harp, Sailor Mercury uses a much stronger, more coordinated water attack, Mercury Aqua Rhapsody to break Fish-Eye's spell and free her mother.

Usagi and Chibiusa arrive in response to Ami's call for help, and when they transform into their Senshi forms the age switch is reversed. The two of them use Moon Gorgeous Meditation to destroy Fish-eye.

PallaPalla watches this through her mirror and is intrigued by their power. Noticing her future mother's strength, courage, and beauty, Super Sailor Chibi Moon realizes that it is not her, but Super Sailor Moon who is the maiden Helios is seeking. She uses the bell to call him again and tells him that the one he needs isn't her, but Princess Serenity. She then runs away, feeling dejected and useless, and Pegasus disappears.

Trivia
Act 40 Yume 2 - Mercury Dream
 * This act contained the first appearances of Guardian Mercury, the Mercury Crystal, the Mercury Harp, Mercury Crystal Power, Make Up, Super Sailor Mercury and Mercury Aqua Rhapsody.
 * in the original anime, the girls switch back due to Pegasus's reversing the spell