This is one of the best episodes of Charmed ever! It is definitely one of my favourites!
I found this episode really funny, especially Piper and Prue! Natalie was really annoying in a funny way.
Anyway, Leo's whitelighter friend Natalie comes to see the Charmed Ones after her charge is killed by a demon, Eames. Natalie is bossy and drives Prue, Piper and Phoebe crazy. The Elders believe that Leo is letting his emotions get in the way of his judgement so they ask Natalie what she thinks. Piper is really jealous of Natalie because of all the time her and Leo spend together and spends most of the episode pissed off at Leo. In the end, Natalie dies by Eames (the demon) and Piper and Leo's engagement becomes official when the Elders take them off "probation".