When Prue is framed for stealing from the auction house and arrested, it is revealed that her boss, Rex, is a warlock. It's up to Piper and Phoebe to prove Prue's innocence and vanquish Rex before its too late.

A band of knowledge-stealing warlocks hunt down a young man who uncovered the location of one of the greatest sources of power in the world. Meanwhile, Prue has her hands full with Jack Sheridan.

Prue begins experiencing the powers of an empath, thanks to a warlock, but she soons loses control. Meanwhile, Phoebe's relationship with Cole becomes turbulent when he tells her he doesn't want to see her anymore.

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.

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.

The Seer plans to steal Phoebe's unborn baby so she can raise the child to become the next Source and prevent the throne from passing on to another demon. Meanwhile, the baby begins to take over control of Phoebe's body, which proves dangerous to Paige.

Piper, Paige and Leo struggle to convince Phoebe, now a mermaid, to come back to her life as a Charmed One, when she decides to ""swim"" away from her problems with Cole. Meanwhile, Piper casts a spell to stop her panic attacks but instead of facing her fear, she suppresses it, endangering herself and her baby, when a sea Demon comes after her mermaid sister, Phoebe. In order to help Phoebe, Paige takes drastic measures and enlists the aid of Cole, and his newfound demonic powers.

When a demon attacks and kills one of the three nympths that protect a lake, the Charmed ones try to help. However, once the demon is destroyed, the nypmphs decide Paige should replace the fallen nymph, and they won't take no for an answer.

Paige is forced to make a deal with a demon, in order to recover her boss's soul. Meanwhile, Piper learns that Wyatt has been sabotaging her dates, Phoebe gets a new writing partner, and Chris and Leo accidentally travel back in time.

When Piper is kidnapped and cocooned by the Spider Demon, and becomes Chris infected with the Demon's venom, causing him to mutate into a spider, Paige, Phoebe and Leo try to rescue them. Meanwhile, Leo finally learns why Chris resents him.

When Paige encounters Captain Black Jack Cutting, an 18th century pirate in search of the Fountain of Youth, the curse on his life becomes her problem. Meanwhile, Leslie manipulates a contest in order to spend time with Phoebe, Leo fights with the creature that caused him to kill an Elder, and a mysterious federal agent comes to town to investigate the Halliwells.

When Daryll's friend is possessed by the spirit of an innocent killed in a fire in 1899, Phoebe and Drake transport themselves back in time to the caberet where it happened. However things go from bad to worse, when they find they cannot travel back to their own time. Meanwhile, Piper convinces Leo they need to take a family vacation.

While attempting to take over the Underworld, a young demon plots to lure the Charmed Ones out of hiding, but when Billie stumbles onto his plot ,she becomes one of his victims instead.

With the intention of helping his parolee get a loan, Henry, along with Paige, go to a bank but instead the parolee decides to take everyone at the bank hostage. Meanwhile, Phoebe and Piper have their hands full when, during his third birthday party, Wyatt turns three of his toys into real people.