Who Robbed the Crane?

The Egret's precious Radjudju diamond has been stolen. Strangely, the chest which held the stone has not been forced and a little water has been put in place of the diamond. What jewel thief could have done this? At the same time, Sherlock has another problem. Babette, Hermione's aunt, has come to the zoo and has decided to marry Sherlock whom she's crazy about.