In suburban Connecticut, upper-class high schooler Amanda (Olivia Cooke) euthanizes her crippled horse with a knife, resulting in charges of animal cruelty. Some time later, Amanda arrives at the home of the more popular and academically-inclined Lily (Anya Taylor-Joy). The girls had previously been best friends but grew apart after the death of Lily's father. They meet under the pretense of hanging out and having a casual tutoring session, but Amanda knows that her mother (Kaili Vernoff) has paid Lily to socialize with Amanda. Lily denies being paid, but Amanda, left emotionless by an unspecified mental disorder, is unfazed. Lily meets with Amanda again, this time voluntarily, and they rekindle their friendship..