When a shapeshifting warlock tricks Prue into a shot-gun wedding in order to steal the Book of Shadows, Phoebe and Piper are lured to the dark side and begin to enjoy their new evil powers.

When Phoebe feels the pain of an injured American-Indian ghost she sees in a deserted town, Prue travels back in time to the mid-1800s to save the man, and Phoebe, from death at the hands of a local thug.

On the day of Piper's marriage to Leo, Prue's Astrally Projected-self adopts an uninhibited, wild personality that threatens to ruin the wedding and place Prue in jail for Murder.

Prue, growing weary of her battles to save innocents and in fighting off the Angel of Death, is forced to turn her back on a dying soul, and must come to grips with her feelings towards fate and the death of her mother.

Mourning the death of Prue, Piper and Phoebe must now come to grips with the loss of their oldest sister, and the loss of the Power of Three. However, The Source discovers an unknown sister - the daughter of Patty and her whitelighter Sam, who had been kept hidden, Paige, the now-youngest Halliwell can restore the Power of Three and reunite the sisters' strength as witches.

Mourning the death of Prue, Piper and Phoebe must now come to grips with the loss of their oldest sister, and the loss of the Power of Three. However, The Source discovers an unknown sister - the daughter of Patty and her whitelighter Sam, who had been kept hidden, Paige, the now-youngest Halliwell can restore the Power of Three and reunite the sisters' strength as witches.

Paige takes the Book of Shadows into her work to cast spells which help her co-workers. Meanwhile, Piper, who is filled with anger over the death of Prue and the recent actions of Paige, is possessed by a member of a supernatural band of vigilantes known as the Furies.

The Halliwell sisters must find a way to release Muses which have been abducted by a warlock who is attempting to build an evil faction in the absence of The Source.