Bentley needs Sly to explore the palace and then find a way to get into the ballroom and see who is at Rajan's party. Sly enters the ballroom via a balcony.
It's now up to Sly to take recon photos of Rajan, the guests and the Clockwerk Wings in order to plan and prepare the next set of jobs required to get to their final objective: steal the Clockwerk Wings in front of a large crowd. The guests include the entire Klaww Gang, excluding Dimitri, and undercover cops The Contessa, Carmelita and Neyla, much to Bentley's concern.
When photographing Rajan, if you look closely, a watermelon will appear at the bottom of his stick when he stops walking.