Cole is after the Nexus beneath the mansion;he must first own the house.He replaces Phoebe with a shapeshifter who convinces Piper and Paige that the only way to solve their problems is to sell the house.
When Piper and Leo begin to have marital problems,Piper casts a spell to allow them to literally see their past together.The spell goes awry when Phoebe and Paige are sent back in time to relive Piper's memories.
The house has been taken over by the spirits of all the demons they have vanquished over the years.The Charmed Ones summon a Witch Doctor,who after ridding the house of the spirits,turns on the Charmed Ones believing them to be evil as well.
When a demon starts killing Sandmen, The Charmed Ones are left fighting their own nightmares. The only way out is to put themselves to sleep in order to confront their own "demons".
Phoebe finds herself constantly saving the life of her new boyfriend when it's revealed that she has altered destiny which will ultimately end in her death. To put the course of destiny right, Piper uses a time travelling Warlock's power
