This video shows how to reach the lighthouse (enter Kingsparrow Fort), enter the Gatehouse, enter the lighthouse elevator, enter the lighthouse and rescue Emily and take out Havelock nonlethal (without killing anyone) and undetected (without being seen). This is the last mission in Dishonored. Note that I am playing on the hardest difficulty without any supernatural or normal upgrades. This means that I don't need to pick up any Bone Charm or Runes or any other loot since I am not going to use them. Note that I also don't use any consumables like sleeping darts.