Cassie Blake is a beautiful and shy, sixteen-year-old girl who moves to New Salem with her mother, to look after her sick grandmother. After being enrolled into a local high school, Cassie meets Diana Meade, a genuine and kind-hearted student who welcomes Cassie to her new school. Cassie also meets Diana's sadistic cousin, Faye Chamberlain, who promptly begins to ridicule and taunt her, all the while taking pleasure in causing Cassie pain.
After Diana introduces Cassie to other members of the circle, they reveal themselves as witches, and that she is one as well. Initially, Cassie refuses to believe them - until Adam shows her how to unlock her magical powers. After Cassie reluctantly joins the circle, Adam, Diana, Faye, and the other members of the coven quickly discover that with Cassie in their circle, they are able to cast spells more powerful than they ever could before.
After Faye is attacked by the Witch Hunters, Jake, Melissa and Adam set out to save her. Blackwell tells Cassie and Diana that the only way to stop the Witch Hunters is to use their Balcoin blood to unleash the Crystal Skull. Diana is reluctant, but Cassie convinces her it’s the only way to help their friend, but she’ll need to tap into her dark magic to do it. Meanwhile, Dawn and Charles are faced with a new way to get their power back...but at a very big cost.
It’s Prom night in Chance Harbor and after Adam uncloaks a crystal hidden in the school, Blackwell tells Cassie she can use her dark magic to find it. When Cassie follows this advice, it leads her to a dangerous discovery. Meanwhile, Faye invites Jake to Prom, despite the fact that he stood her up two years earlier. Adam, Diana, Cassie and Melissa finally make it to Prom but when they lose the crystal to Eben, they end up in a life and death situation. Meanwhile, Dawn attempts to stop Blackwell, who casts a deadly spell on Charles.
When a crystal is magically stolen from the abandoned house, the Circle decides it was the traitor witch working with Eben so Jake calls for a meeting with Isaac to see if they can get him to change sides. Cassie’s loose grasp on her dark magic threatens to destroy any possible alliance when their pursuit of the traitor leads them to the “Creepiest Place on Earth.” Meanwhile, Faye and Jake work together to steal Dawn’s crystal, Melissa and Adam pair up and uncover a new magic trick. Meanwhile, a frustrated Diana reaches out to Charles for help.
To protect themselves from the witch hunters, Jake, Cassie and Faye seek out Jake’s grandfather Royce, to find his family’s crystal and are confronted with disturbing theories about the events of sixteen years ago. Meanwhile, Diana tries to balance her pursuit of the Glaser crystal with Melissa and Adam with her romantic life with Grant, who demands to know what she’s hiding. At the same time, Callum attempts to re-insert himself into Melissa’s life. Charles and Jane plot their move against Blackwell.
Jake gets a surprise visit from an old acquaintance named Samuel, a witch hunter, who has a message for Blackwell about Eben’s surprising next move. Cassie intervenes, forces Samuel to reveal his news and is stunned to find out what Eben is trying to resurrect. Meanwhile, Diana is frustrated that keeping the secrets of who they are is building a barrier between her and Grant. Faye and Melissa agree to help out Adam at the Boathouse and in return get him to help them use their magic to enhance their love life.
