Ariana Osgood, an escapee from a women's prison, is happily enrolled at an elite school. She poses as Briana Covington, a girl that Ariana killed in order to assume her identity. Her life seems finally on track as she has a set of entirely new friends and a wealthy grandmother footing the bills. Ariana has gone to great lengths to secure this new life, including stealing from other students in order to pay off Kaitlynn Nottingham who also escaped with her. However, Kaitlynn shows up as a student at the school due to a large donation made with the money Ariana stole. Kaitlynn poses as Lillian Oswald and Ariana is not happy to see her. The girls wind up as roommates and Lillian begins making demands on Ariana.

Ariana and Kaitlynn are recruited by the secret society, the Stone and Grave. They are each given assignments to complete. Kaitlynn's assignment is to become a hero while Ariana's is to make a spectacle of herself. The problem is that there are five potential members and only four slots in the society. Kaitlynn begins demanding that Ariana eliminate one of girls competing for the slot and promises that she will kill one of them if it becomes necessary. Ariana knows Kaitlynn will commit murder if it suits her and sets out to find another way. She plants a cheat sheet on another of the pledges, Allison, but doesn't realize Allison has a problem with dyslexia and the plan fails.

Ariana begins to develop friendships with several of the other girls, including Brigit who is the princess of Norway. She also forms a mutual attraction with Palmer, who is the former boyfriend of another of Ariana's new friends, Lexa. Ariana denies her attraction with Palmer in public, fearing that she will anger Lexa, who Ariana believes is a member of Stone and Grave. Ariana fears that Lexa might blackball her from the organization. Ariana arranges for Lexa to meet another young man, hoping the two will begin dating, clearing the way for Ariana and Palmer to make their relationship public.

Kaitlynn becomes friendly with another of the potential Stone and Grave members, Tahira, and Tahira soon makes it clear she knows Ariana planted the cheat sheet and that Ariana is a thief. Ariana decides that killing Tahira is the only option left to her and she manages to steal Tahira's eip-pen during an extravagant event hosted at the Norwegian Embassy. Ariana then manipulates the appetizers being distributed so that Tahira eats a snack laced with peanut oil. She almost immediately collapses and it's only then that she realizes her pen is missing. Ariana stands back and watches as Tahira's situation becomes critical but Kaitlynn grabs the pen from Ariana's possession and rushes to save Tahira's life, thereby fulfilling her requirement for induction into the society.

Ariana realizes that Kaitlynn's decision to save Tahira wasn't prompted by the fact that they are friends and that it must mean she has killed someone else. She soon discovers that Brigit is dead, the apparent victim of a tragic fall down the stairs.