Following the mysterious disappearance of Hotaru, Rini goes to her house to find Hotaru missing, and the house completely empty. Trista tells her that Hotaru was gone when she got there, but Rini thinks Trista made her leave.
Darien finds out that Doctor Tomoe works at the Mugen School, so they go over to the school to check if Hotaru is there. Trista and Rini arrive, and Trista says she suspects that Tomoe is associated with the Heart Snatchers.
Mimet targets a physicist named Dr. Sergei Asimov, who will be giving a lecture at Mugen School, but Tomoe tells her the time isn't right. However, she listens in on him and discovers the reason behind his decision; he is tired with Mimet's failures and is giving the job to Telulu, the third of the Witches 5, instead. Mimet later contacts Telulu, using a voice changer to imitate Tomoe's voice and tell her that the project was cancelled. She finishes by saying "Ta ta", which confuses Telulu.
Darien discovers that a building was burned down with Hotaru and Tomoe in it, and they survived without any injury. Serena, Amy, Raye, Lita, and Mina enter Mugen School to look for clues for Hotaru and Tomoe. Mimet enters so she can steal Dr. Ajama's Pure Heart, but Telulu is spying on her.
Hotaru experiences a flashback to the lab explosion. Tomoe was doing an experiment and looking into another galaxy (the galaxy where the Sovereign of Silence is from), when suddenly it caused the device to explode, nearly killing Hotaru. Then, the spirit of a Daimon appeared from the galaxy and possessed Tomoe through his right eye in exchange for saving Hotaru's life.
During Dr. Ajama's lecture, Mimet releases her Daimon, Upasocon, who tries to suck out Dr. Asimov's Pure Heart, but the Sailor Scouts stop her. They fight Upasocon, who releases evil mice after them, but Sailor Mars uses Mars Fire Ignite on them. Sailor Jupiter uses Sparkling Wide Pressure on Upasocon, and Sailor Venus destroys the rest of the mice with Venus Love Chain Encircle after Sailor Mercury locates them. Tuxedo Mask and Sailor Mini Moon arrive. Sailor Moon uses the Purity Chalice to transform into Super Sailor Moon. She uses Rainbow Moon Heart Ache to destroy Upasocon.
Mimet reveals a machine made by Eugeal, and activates it. She glows orange and vanishes, and reappears on the giant TV screen, her size and power increased by the machine. Before she can attack, however, Telulu appears and reveals the reason Eugeal never used the power device; If someone is inside the display unit when the power of the machine is shut off, they will be automatically sealed inside it forever. Mimet begs Telulu not to pull the plug, but Telulu does anyway, and Mimet falls into nothingness. Telulu disappears, and the Sailor Scouts are confused as to why the Witches are turning on each other.
- Serena Tsukino/Sailor Moon- Linda Ballantyne
- Rini Tsukino/Sailor Mini Moon- Stephanie Beard
- Amy Mizuno/Sailor Mercury- Liza Balkan
- Raye Hino/Sailor Mars- Katie Griffin
- Lita Kino/Sailor Jupiter- Susan Roman
- Mina Aino/Sailor Venus- Emilie Barlow
- Darien Shields/Tuxedo Mask- Vince Corazza
- Amara Tenoh/Sailor Uranus- Sarah Lafleur
- Michelle Kaiou/Sailor Neptune- Barbara Radecki
- Trista Meioh/Sailor Pluto- Susan Aceron
- Hotaru Tomoe- Jennifer Gould
- Security Guard- Tony Daniels
- Dr. Sergei Asimov- Vince Corazza
- Upasocon- Loretta Jafelice
- Mimet- Catherine Disher
- Telulu- Kirsten Bishop
- Doctor Tomoe- Jeff Lumby
- First and last appearance of Daimon Upasocon
- Final appearance of Mimet (though her death is shown again in the next episode)
- Doctor Tomoe's full name is Souichi Tomoe
- It is revealed that Doctor Tomoe is possessed by a Daimon
- Telulu appears more clearly in this episode, with her face shadowed
- This is the second time a monster of the week and the major villain that sent her are killed in the same episode. The first was in Birthday Blues Part 2. Except that Kaorinite came back to life. The only other times a monster of the week and a major villain die in the same episode are when the monster of the week is the one who kills the major villain (who has usually turned good by this time), which happens twice.