Cassie Blake (born March 28, 1995) is the main female character and protagonist of The Secret Circle. She is the daughter of Amelia Blake and John Blackwell; the best friend and the paternal older half-sister of Diana Meade, and the paternal older half-sister of Four unknown half-siblings; the ex-girlfriend and best friend of Adam Conant; and a member and the leader of the Chance Harbor Circle.
Cassie was a happy, normal teenage girl until her mother Amelia died in what appeared to be a tragic accidental fire but not such as an accident. Orphaned and deeply saddened, Cassie moved in with her warm and loving grandmother Jane in the beautiful small town of Chance Harbor, Washington - the town her mother left so many years before - where the residents seems to know more about Cassie than she does about herself. As Cassie gets to know her high school classmates, including sweet-natured Diana, her handsome boyfriend Adam, brooding loner Nick, mean-girl Faye and her sidekick Melissa, strange and frightening things begin to happen. When her new friends explain they are all descended from powerful witches and they've been waiting for Cassie to join them and complete a new generation of the Secret Circle, Cassie refuses to believe them - until Adam shows her how to unlock her incredible magical powers. But it's not until Cassie discovers a message from her mother in an old leather-bound book of spells hidden in her mother's childhood bedroom, that she understands her true and dangerous destiny. What Cassie and the others don't yet know is that darker powers are at play, powers that might be linked to the adults in the town, including Diana's father and Faye's mother - and that Cassie's mother's death might not have been an accident. But the more time passes by, the more Cassie gets confident of herself and develops her incredible potential.
Cassie is a member of the Blake family and the Blackwell family.