zankou has the book of shadows and he wants to kill the sisters with it. this episode is one of the best in charmed 8 year run. It's exciting and the writing was also very good and when they were in the house you actually thought they were going to die.
This was the best and most exciting episode of season 7 and it is re-watchable. I hace watched it at least 5 times and i am still not bored with it. This was a great season finale.
overall: This is a really good episode of charmed and most people who watch it will enjoy it.