With Piper growing more concerned that Leo will never return, Prue and Phoebe try to save a little girl and a fairy princess from evil Trolls. When Prue and Phoebe need Piper's help, her concern with Leo causes a spell to backfire, placing the girl in danger.

Prue & Phoebe have their hands full when Piper is possessed by the spirit of an evil witch, on the day of her high school reunion.

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.

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.

Amongst newlyweds, Phoebe & Cole and already-married, Leo & Piper, Paige begins like a fifth-wheel but she continues her suspicions about Cole. Meanwhile, the Source plots to impregnate Phoebe with his evil spawn.

Phoebe accepts her new role in Cole's life, but she still sets out to save an innocent after she has a premonition and even seeks her sisters' help in protecting the man. Meanwhile, Piper's heart doesn't seem to be in it as she prepares to defend her family against any new threats from the underworld.

Cole and Phoebe both fall under the spell of the Siren, who lures husbands to her and entrances their wives to follow with the intent to kill, leaving Piper and Paige to figure out how to save Phoebe. Piper, upset with Leo because he does not understand the challenges of being pregnant, and Leo, frustrated that Piper does not realize the demands of being a Whitelighter, have their personas switched magically by their unborn child.

After kidnapping Phoebe, Cole sends a shapeshifter to assume Phoebe's identity to help him manipulate Piper and Paige into giving him ownership of the Manor, allowing him access to the powerful Nexus located beneath the house. Meanwhile, Phoebe plans her escape, and Cole gets Paige arrested and ensures that Piper's club fails to pass health inspections in order to keep them distracted.

The Charmed Ones must protect Piper's son from two demons, but the baby has a few surprises of his own. Meanwhile, Paige goes undercover as a bounty hunter and Phoebe's future with the newspaper is threatened by the new owner.

When the mythic Gods, the Titans, are released and kill all the elders, Leo is forced to take over. Meanwhile, a mysterious Whitelighter from the future guides the Charmed Ones when Leo gives the girls the ultimate power to vanquish the Titans, recreating them as Greek Goddesses, despite the risk that they will be seduced by their vast new powers.

Under the pressure that the Halliwell sisters will discover his evil plot, Gideon conspires with two demons to make Piper, Phoebe and Paige part of ""Witch Wars"", a new demonic reality television show where demon contestants compete in a series of contests to hunt down the Charmed ones.