The season 4 opener, "charmed again parts 1 + 2" are extremely well written. The acting is also great with newcomer Rose McGowan playing lost list sister Paige matthews, who is discovered to have the powers to orb, heal (with help and to summon objects.
This is one of the episodes I actually enjoy the character or Phoebe and the whole show seems to be much more interesting with Paige instead of Prue. Charmed Again is the episode that got me hooked. I reccomend it to anyone! A+