Letter from the Chief Thief

This was found in combat against the burglars at Milone's house: Milone the jeweller has just created a very valuable jewel. Steal it by whatever means necessary. Fortunately, Milone gave them a copy, but it's no thanks to you. On the back of the message, though, there is a guide to their hideout. Revenge beckons, but you won't be able to do it alone.