"Steal Chamberlaine's plans" is a mission objective in Sequence 7 / Memory 01: We Demand A Parlay
Walkthrough[edit]
Climb up onto the top of the fort. Head over to the Southeastern corner and look down. You will see 2 Soldiers below you. Kill them with a Double Air Assassination then head over to the nearby cannon. Look along the wall to attempt to spot the next Gunner. If not spotted, advance toward the flag at the corner, Dart Gun at the ready. If spotted, tag him with a Sleeping Dart then move in and knock him out. Backtrack now to the break in the wall toward the courtyard. Look down for the hay cart. Wait for the patrol to go by then jump down into it and take out the nearby guard. From here you can easily dart over to the Alarm Bell and disable it after the next patrol goes by it. Be sure to tag the Guard on the Southeastern wall with a Sleeping Dart to stop him from noticing you. Move to the bell and waitfor the Gunner to lose interest in you. After that disable the bell.
Head across the way to the West carefully. Get to the wall and use that as cover until he turns his back. When he does, make a run for the plans. Grab them to end this memory.
