As far as Fashionably Late is concerned, the Azdariz Diamond is just another jewel her husband Filthy Rich has bought for her. So when she loses it, she confides in Rarity that she'll be putting an announcement in the paper: whoever finds the diamond can keep it.
To Rarity, however, the Azdariz is the finest gemstone ever produced in Equestria, and she's determined to keep it from falling into less appreciative hoofs. Donning the Mare-Do-Well suit, Rarity slips into Ponyville's midnight shadows to track the diamond down before the announcement gets published.
Then Rainbow Dash gets involved. Then things get complicated.
This story was awarded 6th place in the April 2015 Writeoff Association contest, "Great Expectations," and the cover art was commissioned from marking.