The "Charmed Ones," three sisters in San Francisco who are the most powerful good witches the world has ever known, have used their powers and "The Book of Shadows" to keep themselves alive and save innocent souls. But the power of three has been broken and eldest sister, Prue, is gone forever. The remaining sisters, Piper, the earthy and creative middle sister, and Phoebe, the free-spirited youngest, search for a way to stay alive and strengthen their fragile bond. The sisters are renewed with the revelation that there may be another sister that they never knew about -- one who could reunite the power of three.