- Don't get into conflict
- Lockpick one door
Looks like the plan backfired a bit and Robespierre has been taken into custody, making Arno’s job to find him that much more difficult.
Follow Elise through the streets until you come across the dead guards and enter the area, turn left, and then right down an alley to find a survivor. After the scene you’ll need to search the area for other survivors until you find Robespierre.
Start by taking a left onto the street and then right down the first alley to the first guard for a quick conversation. Turn left again and run past the lift and then turn right down an alley near the underground entrance to find the second guard.
Robespierre is nearby, but in order to help with the no conflict optional objective I suggest you climb the buildings before you approach the search zone for a scene.
The trick to following Robespierre in the rooftops is not to make quick direction changes, as he has a tendency to weave in and out of the alleys, and instead try and head in a general direction. Use the ropes and roofs to follow him and stay off the ground, but don’t worry if the game starts to tell you to reduce your distance to Robespierre.
If you do lose Robespierre a search zone will be placed nearby, which you can head to in order to continue the story.
After the scene you’ll be on the roofs just outside the restricted zone, but rather than take a direct approach your best option is to head around the left side of the building and enter it through the side. Make your way left across the rooftops and then cross the rope to the south and climb up to kills a sniper on the roof.
You can now walk to the wooden beam and jump to the building to climb the left side of the tower to a landing that overlooks another sniper. The sniper is too far away to air assassinate, and there is no point in wasting your Phantom Blades, so jump to the slanted roof behind him and then quick press Square / X to air assassinate him.
Cross the landing and hang from the ledge above the next patrol and shimmy over to kill him, or wait for him to return closer to the landing, and then hop in the window and sneak up on the Brute by the locked door. You’ll need good timing and the lockpick ability to be maxed to even have a chance at unlocking this door, but it’s required for the optional objective.
Enter the next room and use Eagle Vision to identify the three guards in the room with the door between you and Robespierre. The two guards by the door and desk are stationary, leaving the only worry the Brute that patrols between the two desks. I suggest using your Phantom Blades to headshot the Brute and then wait for the two other guards to reset before you sneak in and kill the one at the desk, followed by the one at the door.
You can now interact with the door to complete the mission with a brutal, but much deserved, scene.