- Don't get into conflict
Outside the De La Serre residence you can continue the story to find out that the master will be out for a while and Elise is at a private party. Time to crash the party, but first you should head upstairs to examine some glowing items for some minor commentary and then slip the letter under De La Serre’s office door.
After Arno makes a quick change of clothes and sneaks into the gala you’ll need to use the crowds to hide from the guards and avoid being kicked out again. Head around the left side of the blue tent full of guards and head for the side of the building that is brightly lit with two red banners and climb up into the building.
Head to the next room and wait for the guard to move over by his friend at the window before you pass through, hitting L2 / LT to enter Stealth Mode. The next room is empty and you can head straight into the next room and take cover on the couch by pressing X / A. Wait for the guard to take position by either the fireplace or the bookshelf before you exit cover by pressing X / A again and then exit the room.
The empty hallway leads to another room with a guard, this one surrounded by a set of tables laid out in a U shape, so take cover by the first table. You need to stay in cover and switch from one table to another by holding the Left Stick and pressing X / A to switch the next cover spot. Wait for the guard to turn around and head for the window before you pass around the second table and then hop out the window and across to the other balcony for a scene.
Make your way around the area, using Eagle Vision to spot Elise and her father, and then enter the ballroom for another short scene. Once again you will find yourself following Elise through the beautiful French interiors until you trigger a scene.
Afterwards, hop out the window and down to the ground floor an make your way into the room with a bunch of cloth covered furniture. One of the guards here will walk off and leave, but the other stays and patrols back and forth between the furniture. Wait for the guard to turn his back and make your way around the room.
Depending on how long you take the next guard may already be in position at the fireplace, meaning you can cross safely into a dining room. Continue to follow the guard, using the banquet table for cover, and then veer right in the next room full of cloth covered furniture to safely exit the palace for a scene.