Abandonment and Escape
Dumain, a demon in league with the Triad, attempted to and succeeded in convincing the magical community that the Charmed Ones had turned their back on them by using past incidents, as well as a spell that made the sisters only concerned with their own needs, the Magical Community abandoned them, the sisters were forced to hide out in the Underworld. After Billie and Christy forced them to flee following a battle gone wrong. the girls eventually found refuge in Phoebe's condo. There, they were contacted by former Triad servants Nomed and Zohar, who wanted to work with the sisters to destroy the Triad. The demons then convinced the sisters that the only way to defeat the Ultimate Power was to summon the Hollow.
Summoning the Hollow
After countless draws with the Charmed Ones, the Triad came to a decision for the Jenkins sisters to summon the Hollow to kill the sisters. Summoning the Hollow takes a powerful force. Although the Charmed Ones were able to summon it themselves using the Power of Three, The Jenkins' had to get the help of Wyatt Halliwell, Piper and Leo's oldest son, as it would take "Charmed power" to summon it. Dumain shimmered over to Victor's apartment where Wyatt and Chris Halliwell were staying and convinced Wyatt that he was needed to help his mommy. Billie and Christy held hands with the young boy and combined their power with his in order to summon the Hollow. Once acquired, they stole Wyatt's powers so they'll be evenly matched with the Charmed Ones. As that the Hollow feeds on power, they were about to steal Dumain's powers, but he shimmered out when Christy shot fire from her eyes.
The Charmed Ones
With the help of two demons, Nomed and Zohar, they were able to find out the Triad's plan to summon the Hollow to make Billie and Christy almost invincible. Piper suggested that they should get the Hollow before Billie and Christy do. Paige was skeptical, remembering what it did to The Source and Cole, but Piper was convinced that the Jenkins were trying to steal the Charmed Ones' powers. Paige and Phoebe thought summoning the Hollow was too risky, but Piper argued they could vanquish Billie and Christy and say the spell to send it away before it infects them. The alternative, she said, was letting the Jenkins have it which would mean certain death. Nomad and Zohar said they had to vanquish the Triad once and for all as well and the Hollow would give them the power to do it. When Piper wondered if they would have to worry about renewed demon attacks, Nomad replied that the Charmed Ones had severely decimated their ranks over the past eight years. Apart from the Triad, the few demons that were still alive were not nearly strong enough to take on the Charmed Ones head-on, and they'll only be able to regroup when the next generation of witches takes over. Piper saw another apparition of Leo which motivated them to summon the Hollow. Then, they killed Zohar with his own Energy Balls and orbed to the Triad and killed them with powerful lightning bolts.
The Final Battle
After vanquishing the Triad, the Charmed Ones orb to the manor. They turned around to see The Jenkins Sister's coming down the stairs. Both set of sisters are surprised that neither of them have potions. The Battle then starts to begin, Billie and Christy throw fire, whilst The Charmed Ones reply with lightning. The power slowly starts to trash the Manor, hitting many objects like lamps and the grandfather clock. The power is so strong that it blows the Manor up; killing Phoebe, Paige and Christy.
When Piper finds Phoebe dead, The Angel of Destiny returns Leo. Destiny tells Piper that the battle wasn't meant to end this way. She suddenly hears a moan, thinking it's Paige, she follows the sound, she realizes it's actually Billie and begins to beat her up, angry at her for killing her sisters. Leo tries to get Piper to stop beating up Billie, when he eventually does, she runs off and Piper tries to kill her using her Molecular Combustion power, but doesn't succeed. Leo tells Piper that they have to go. They take refuge in Phoebe's Condo. Piper tells Leo that she will find a way to bring her sisters back to life but doesn't know how yet. They go to Victor's apartment to tell him that Phoebe and Paige is dead. Victor mentions Coop and asks if he could help. Piper calls Coop down and he beams in. Piper tells Coop that Phoebe is dead and may be able to bring her back if he lets her borrow his ring. The Ring enables the wearer to go back into the past, Piper is convinced that she will be able to use it to go to the exact moment where the Battle starts to begin and to banish the hollow back. Unknown to them, Dumain is telling Billie to use her power of Projection to project herself into the past, to save Christy and the Triad.
Piper and Leo, with Coop's ring, go back into the past. But instead of going back to the time when the Battle had begun, they were transported to 1975. They see a past Patty and Victor making love. Patty, startled, attempts to freeze them, but it only works on Leo. Patty notices that Piper didn't freeze, she tells her mother that she's her daughter, from the future and that the man beside her is her husband Leo. Piper tells her mother and father that there was a great battle in the future, killing Phoebe and Paige. Patty explains to Piper that if they were able to get Grams, they might be able to re-create the Power of Three in theory to banish the hollow back. Instead of beaming to their Grams, they accidentally get teleported to 2050, where Piper is the "Grams" of the family. Elderly Piper and Elderly Leo tell them that they have to focus with their heart, not their head. Patty, Piper and Leo beam into 1982, where they find a Past Penny and a 10 year old Piper talking to each other. Grams tells young Piper that she's special in her own way. Grams hears a sound and sees Piper, Leo and Patty. Patty comes out and tells her it's just her but Penny faints because of the fact that Patty was dead in her time.
Billie projects herself back into the past at the Manor, just as the past Billie and Christy arrive. She warns them, but past-Billie sends present-Billie flying into the wall with her telekinesis and goes on to fight. The battle starts to play out as before but then Piper, Grams, and Patty arrive to cast a spell which drives the Hollow out of the five girls. Present-Billie and Piper merge with their past selves; time has caught up with itself. Billie and Christy teleport out with their potion. The Angel Of Destiny arrives to take Leo back, because the final battle has not been fought.
Back at the manor, Chris and Wyatt explain that Wyatt lost his powers in the middle of a demon fight and they came back to the present to find out how. Coop arrives and Wyatt recognizes him as “Uncle Coop,” leaving Phoebe confused. Chris, Wyatt and Patty orb to Victor's apartment.
Dumain and Christy find past-Dumain talking with the Triad. They try to warn the Triad that they have to get the Hollow before the Charmed Ones do. Billie came to The Manor and tells them that she was tricked, and she needs their help to stop The Triad. Just then, the Charmed Ones and Billie arrive as well. The Charmed Ones vanquish the Triad with potions, then Piper blows up present-Dumain. Past-Dumain starts to shimmer away, but Piper blasts him in mid-shimmer and blows him up as well.
The Halliwells explain that Billie brought them back by projecting herself to Christy. Before Christy can react, Paige orbs the ring from Christy's finger. Christy accuses Billie of betraying her. Billie begs Christy one last time to give up evil and come home. Instead, an enraged Christy launches a huge fireball at them. Billie telekinetically deflects it back, vaporizing Christy; realizing she has just killed her sister and that her entire family is gone, she breaks down in tears as the Charmed Ones comfort her.
All the Halliwells are reunited at the Manor and Wyatt has his powers back; he happily orbs to his mother's side to show them. They reveal Billie has gotten back her own way and needs to be alone for a bit. The Angel of Destiny arrives with Leo and reveals this was how the battle was supposed to end which means that only Christy was supposed to die. Victor and Patty arrive with the children and Coop reveals he can take Patty and Grams back and make sure they won't remember what they've learned. Patty reveals that Victor told her Prue is dead, and it's one thing she wants to forget. Wyatt and Chris from the future told Phoebe and Coop that their love wasn't forbidden and that The Elders sent Coop in hope that Phoebe will fall in love with him. Everyone shares a happy moment before going their separate ways. In the end, the Charmed Ones edit the book and write everything what happened to them to proceed to other generations.