Fulfillment, harmony, completion
The nun smiles as the man thanks her profusely for her advice. He had found himself led astray and not knowing which way to turn, but now he feels a great burden has been lifted. She hugs him and wishes him well.
Once he has left the room, the nun reaches into the sleeve of her robe and removes a long knife. She stares at the reflection of the candles on the blade before going to look for a victim. She had just performed a good deed, after all, and the universal scales must be balanced.