Assassin's Creed IV: Aveline Walkthrough Part 3 – “The Fort” Part 2
Once in the barn, make your way over to the North and take the stairs up. On the upper level, deal with the 2 Soldier and then head for the open door to the balcony. Head to the North and jump over to the house, immediately crossing over to the Northern. Go from the house to the Stalking Zone just beyond it. With some patience you can take out the 2 patrolling guards who come by you or just wait for them to go by then head to the East across the wall using the crates. Just follow the course straight on until you are brought far side of the fort. Wait for the Soldier below to be facing away then head to the West toward your objective. Climb up onto the house and cross over it to jump onto the hay beyond it. Now wait in there for the pair of guards to either pass you by or present their backs. Now rush over and sabotage the alarm bell then duck into the Stalking Zone you passed. Wait for the final guard in this area to present his back. Move in and deal with him after that. Now turn toward the marker and climb up the scaffolding onto the house.
In the middle of this area you have 2 more Soldiers. Move to the edge of the house carefully. You can assassinate one of them and likely take out the other without much trouble. Just go over to the prison after that. Deal with the 2 guards and head inside. This will trigger a cutscene.
After the cutscene, ignore the guards and turn to the Western wall and climb up it. There is also a ladder to the right you can use. Go for the open door to the balcony. Just rush out to the West and ignore all the enemies and just chase after Patience. Get over to her and defend her after the next cutscene. Get a kill streak going quickly to deal with everyone that comes after her.
When the fight is over she will once again run. Head straight through the gate and up behind the far house. There just go behind the house and over to the cellar entrance. The two women will talk in a cutscene. Patience offers Aveline a deal: her charm for her acceptance of Conner's offer. The two seem to agree on this and then it is onto the final memory of the sequence.