Amy goes over her birthday (September 10) and some of her important likes and favorites. However, she goes not like love letters. She finds one in her locker and breaks out into a rash. She explains to Bunny her hives are caused by stress. When she gets a love letter, she is embarrassed and shocked, but mostly she does not have time for dating during all the studying for high school entrance exams.

After school, Amy is fuming about the practice test score rankings. She uses the alias "Mercury" but is always tied by the person using "Mercurious" as their alias. Both of them have been getting perfect scores. The girls are impressed, but kind of scared. Lita says breaks are important as well as studying and invites Amy to come with the rest of them for a break tomorrow. However, Amy refuses, determined to study and take another practice exam.

Amy thinks about this "Mercurious" her rival. She knows nothing about them, but is determined to win and signs up for all the practice and studying she can.

As she continues studying, the girls notice Amy is beginning to look worn out. They figure it is because of Mercurious, who continues to tie with Amy. She thinks about how smart Mercurious must be, and Mina comments it is like she's in love. Amy wonders if this is her "first love."

At the Fruit Parlor, Mina is determined to find out who Merurious is, and bring him together with Amy. Only she does not know how to trace him out. At school, Bunny realizes Melvin may know something and questions him about the mysterious Mercurious, who turns out to be his friend.

Amy goes to another exam prep session, but is worn out and falls asleep on her books. She goes home to rest when the spirit of the building D. Zire follows her.

The other girls go with Melvin and meet his friend Mercurious.

As she is walking to school in the morning, Amy collapses, and Bunny takes her to the nurse's office. Amy only has a cold, and stays to rest in bed in the office. D. Zire starts attacking Amy with love letters, and her knowledge starts leaving her brain as the letters hit. She thinks the spirit is Mercurious, whom she reasons to be her enemy. Amy transforms and attacks, killing the spirit, and then passing back out again.

After school, Amy overhears that her friends saw Mercurious, and ask what he looks like. Mina pulls out a poster of a pop star to illustrate, however, he actually looks far more like Melvin.