In this episode, we are first introduced to Usagi Tsukino (or Serena in the dub) who is a somewhat average high school girl - she lives with her mom, dad, and brother, goes to school and hangs out with her friends. She is also somewhat clumsy, unrefined, gets bad grades, and is always late for class.
Usagi saves a purple cat with a crescent moon mark on its forehead from being tortured by some kids. Later in the episode, she finds out that the cat's name is Luna, and that Luna can talk to humans. Luna is also the one who gives Usagi her beautiful broach that allows her to transform into the magical girl heroine, Sailor Moon.
We also meet Queen Beryl and her minion Jadeite. Jadeite sends a monster named Morga to take over a jewelry shop owned by Usagi's best friend (Naru/Molly)'s mother. The monster ensures that jewels are being sold very cheaply in the shop and that everyone is buying them. Before long, it is revealed that the jewels are sucking up human energy to collect it for Queen Beryl.
Usagi gets caught up fighting with the monster, and Luna convinces her to use her broach to transform into Sailor Moon. While Usagi is scared out of her mind and does not really know what is going on, she follows Luna's instructions reluctantly. Morga sends out the newly possessed humans to attack Sailor Moon. Sailor Moon is consequently outnumbered and essentially getting her butt kicked, when a red rose flies in front of the monsters. A masked man in a cape and tuxedo (Tuxedo Mask), saves Sailor Moon, allowing Sailor Moon to use her "Moon Tiara Action/Moon Tiara Magic" attack, killing Morga. Tuxedo Mask tells Sailor Moon that he will always fight by her side.
The next day at school, everyone is convinced that the whole event was all just a dream...that everyone at the school happened to have.
Burdened with the new task of being a heroine of justice, Usagi seems neither able or willing to play the part.