The series narrative follows the four Halliwell sisters—Prue, Piper, Phoebe and, later, Paige. They are the culmination of the most powerful line of good witches in history. The sisters, despite being perceived as normal women by the non-supernatural community, are known as The Charmed Ones in the magical community, whose prophesied destiny is to protect innocent lives against evil beings, such as demons and warlocks. Each sister possesses unique magical powers that grow and evolve, while they attempt to hold normal working lives in San Francisco. Keeping their paranormal identities separate and secret from their ordinary lives forms part of the series' tension and challenges, with the exposure of magic having far-reaching consequences on relationships, and having resulted in a number of police and FBI investigations throughout the series.