Board Thread:Character Discussion/@comment-26229833-20150903165256/@comment-91424-20150903182809

This is what is said in the episode:

Hook: "The Dark One. He must be stopped. You've spent more time with him than anyone. There are rumors of a magical weapon that has the power to kill him. (...) I need to know what that weapon is and where to find it." Belle: "I don't know what you're talking about and I have no idea how to kill Rumplestiltskin." Hook: "You don't?" Belle: "No! And nor would I."

So either the writers made a mistake, or Belle is lying to Hook.