Charmed Season 4

Mel and Maggie Vera suffer a shock when their mother dies suddenly, but before they have time to heal from their loss, another surprise shows up on their doorstep in the shape of an older sister -- brilliant geneticist Macy -- whom their mother never told them existed. The emotional stress takes its toll and the girls begin to exhibit impossible new abilities. An explanation comes from an unexpected place: the new chair of the women's studies department. Harry Greenwood reveals that the three are powerful witches, and he is their whitelighter, there to advise and guide them as they battle dark forces.