The map itself should be self-explanatory. There is a crypt and a hidden escape route. The principal exit is in the right hand corner. The other route could lead back to the mansion or even further underground. You can also just ignore it in your game if you want.
I thought about the following way to use this setup in an actual game. The funeral went through without much trouble and the noble was ready to escape but unbeknownst to the noble and their allies, a monster has inhabited the cave preventing the noble from getting out of the crypt. To make matters worse, there is a honor guard near the grave for at least a few days more. The players are then hired as outsiders to get the noble out of the crypt before it becomes the noble's actual grave. This could also act as an intro to a longer campaign. The noble might have a world shattering reason to fake their death. Perhaps the noble is actually a heir to the throne and decided to disappear before their enemies would make a move.