Content warning: death, murder, mention of child sexual abuse

Lisa is a twelve-year-old student at an all-girls school, where she is best friends with Annie and Caroline. Together they form a group called the Teacher's Angels, made up of girls who score perfect on their tests.

When Lisa scores a nine out of ten on a math test, she is kicked out of the group and humiliated by her former friends. Lisa, pleading innocence, appeals to the math teacher, the recently widowed Mr. Herwin, who claims that the answer to the question Lisa got wrong is 45- while Lisa's answer looks like 43. After again being humiliated by her former friends, Lisa sings an aria about how she is in love with Mr. Herwin, but he won't change her mark or look at her. Lisa grows desperate for his attention.

The next day at school, Annie and Caroline see Lisa making lemonade and weasle their way into getting some. Mr. Herwin is close by. When the girls have finished their drinks, they retire to the tall oak tree to prepare for their upcoming test. Once there, they are enveloped by a wave of sickness that burns the inside of their stomachs and weakens them. They begin to panic. Beneath the oak tree, Mr. Herwin finds the two girls dead as we hear Lisa in the distance singing a rhyme while skipping rope.

Mr. Herwin confronts Lisa with his conclusions about the girls' deaths and explains that he'll have to turn her in. Lisa, unfazed, tells him that she's reported to the principal that Mr. Herwin likes to "touch" little girls. Mr. Herwin is flabbergasted.

Confused as to what to do, Mr. Herwin is visited by the ghosts of Annie and Caroline who beg him to avenge their deaths and send them to heaven. Mr. Herwin calls Lisa back and tells her that her accusations are lies and that he can't protect her. Lisa gives him a valentine declaring her love but Herwin will not be swayed. Lisa tells Mr. Herwin that it's possible she sold poison lemonade to Mrs. Herwin and that's how she died so suddenly. Shocked, Mr. Herwin cannot fathom the little girl's actions and descends into madness while claiming his innocence.

A wildly varied and rhythmic score evokes the energy of this adolescent classroom and Lisa’s obsessive need for perfection - at all costs.