Rewards: Pounds: 900 (+125), EXP: 500 (+150), Extra: Outfit - Lady Melyne's Gown
Challenges: 1. Perform a Leap of Faith in a haystack while on a zipline. 2. Counter all of Lucy's strikes.
This is a mission in which you'll want to do only with a fully stocked inventory. At the top of the building where you start, look down and spot various police officers. There are way too many to take out with assassinations or combat, so you'll have to improvise. The monument is guarded from all sides, but a crowd is trying to push towards the monument on one side. Move over the building to get closer to this part of the town square and perform a knife headshot on the two police officers holding the crowd back (it may take up to two knife headshots, and one of them might need to move closer first to the body of the downed officer in order for you to hit him - the rectangle always turns red when it'll hit its target). If more officers come investigate, preferably also take them out with knife headshots. Don't be seen at any time; if your stealth circle turns yellow, quickly back away until you're good to go.
With the most important police officers out of the way, the crowd will flood the square. Climb down and sneak through the crowd to reach the area below the podium and inspect the empty hole. Climb to the top of the monument afterwards, or alternatively climb one of the buildings and use the rope launcher from there to get to the top of the monument. Reach the waypoint for a small scene.
Use the rope launcher to make a zipline directly over the haystack and perform a leap of faith from the zipline. My game never lets me accomplish this, so it seems it's very unforgiving with button combinations. If anyone knows how to exactly pull this off, please do inform me so I can add it into the guide. Before you continue, consider making a quick detour to the nearby shop owner to replenish all your knives. This may come in handy soon.
Afterwards, grab a carriage and ride to your next destination. Climb the building and use eagle vision to locate the golden panel on the middle of the structure, on a statue. This is a puzzle that's almost an insult to the intellect. All you have to do is align the same icons so all adjacent pinwheels have the exact same icons facing each other. Simply move to the waypoint on the cathedral tower and enter through the open window. Inspect the artifact to start a boss fight with Lucy Thorne.
The most tricky part of this fight is to counter all of Lucy's attacks during a special attack sequence. This is part of a challenge; don't mash the counter button but press it once, when her health bar glows yellow. It's difficult to pull off and that is entirely the fault of the programmers, who failed to give a better indicator on when to actually counter. In any case, during the first phase of the fight, immediately starts punching Lucy and try to get in as many gunshots or knives as possible, quickly draining her health. When it's down to 50% she'll start using the combo, granting you multiple opportunities to block all hits as long as you don't finish her off. Beat her down to roughly 20% of her health bar and a scene is triggered automatically.