The page below of our Assassin's Creed III Remastered guide contains a walkthrough on how to find Captain Kidd's treasure in Fort Wolcott.
Optional objective: Perform ledge assassinations - 3.
After obtaining the first Peg Leg treasure, return to the man at the shore to learn the localization of Fort Walcott. You will need to sail there with your ship.
After reaching the destination, start moving right along the rocks and climb to the top of the tower.
There you will be able to perform the first ledge assassination. Just press the attack button while hanging below the enemy.
Kill him and head up. Connor will automatically ride along the line to the nearby warehouse.
Approach the first enemy there from behind and stick a hidden blade into his back.
The next soldier can be found on the lower level. Wait for him to turn his back to you and jump onto him from the balustrade.
The further road leads left. Climb onto the wall there and go through the hole on the right. The second part of the warehouse is guarded by three soldiers. Just like before, you need to get rid of them without raising an alarm.
Wait below the roof for the soldiers to turn around and jump down into the hay pile. From it you will be able to assassinate the first enemy.
Afterwards hide behind the wall on the left, whistle onto the second enemy and kill him when he approached you.
The third enemy is directly above you, walking along a small wooden platform. Climb there and, while holding onto the balustrade, wait for the soldier to appear. As he turns around, kill him from the ledge with the hidden blade. That way you will come closer to a full synchronization.
With the area clear, climb above and turn left. From there you will be able to access the further part of the warehouse by jumping between the equipment hanging from the ceiling.
To move on, jump to the other side of the small room and climb onto the second window on the left. From there you will be able to jump to a hole in the wall by holding down the free run button and pressing jump.
Pass through the room full of soldiers by jumping between the chandeliers.
That way you will reach another guard. Jump to him and kill him from a ledge to get full synchronization.
By the next corner, wait for the walking enemy to turn around and quickly kill him and his companion.
You can now whistle at the other one and stick him a hidden blade from behind your cover.
To eliminate the two enemies below, equip the hidden blade, jump onto the balustrade and aim so that both enemies are lit. Press the attack button and Connor will eliminate two targets at the same time.
After clearing the room, examine the hints in the cell on the right to obtain the first piece of the map.
Optional objective: Limit health loss - 33%.
Optional objective: Completed all the constraints in one playthrough.
Afterwards you will be attacked by one of the soldiers. In order to defeat him without losing any health, dodge his powerful attack, approach him from behind and knock him down with the jump button. He will be an easy target on the ground.
Optional objective: Achieve minimum kill streak - 3.
Keep running forward while avoiding the flames and head towards the green point.
At some point you will bump into another group of enemies. For full synchronization, try to perform a kill streak before the enemy with the axe approaches you. He's unfortunately resistant to quick counterattacks.
With the last soldier dead, keep running to the left until you reach a window from which you will be able to jump down into the sea. Soon afterwards the mission will come to an end.