Meeting with Samuel at his boat | Mission 5 - Lady Boyle's Last Party Dishonored Guide
Last update: 11 May 2016
New Main Quest: Escape back to Samuel's boat
New Optional Quest: Knock out Esma Boyle and deliver her alive to the basement
Regardless of how you eliminated Esma Boyle (by murdering her in front of everybody, killing her or knocking her down in her bedroom) you need now to return to your starting point. You'd better not go through the location you did to get here. Instead, use the service staircase again to reach the kitchen (the above screenshot). If Esma was murdered, you can go ahead right away.
If Esma is only knocked out, you either need to eliminate all of the people in this location, or use the right power. In the latter case, the best would be time hold.
Another step is concerned with reaching the basement and the passage towards it is to the right. Make use of the switch on your way, and reach the main part of the basement. If you are carrying the body of the unconscious Esma, approach Lord Brisby, standing n the boat, and receive his thanks as well as his assertions that the woman will come to no harm.
In order to leave the Estate area, you need to take the door to the sewers (the above screenshot). After you get in a new location, look around for gold and jump into the water.
Eventually, you need to reach the circular valve handle and interact with it, which will unlock the passage for you. DONOT hurry with reaching the spot marked in the game because instead of Samuel you will meet there a tall boy. Read about the current quest.
New Main Quest: Samuel has moved! Find him - past the canal gate
New Main Quest: Talk to Lord Pendleton at the Hound Pits Pub
In order not to be seen by the tall boy, you need to dive, and then get to Samuel. You'd better not stop anywhere in order not to be attacked by piranhas. You can safely resurface only after you get near Samuel's boat, and during the conversation with him, confirm that you want to leave (the upper-right dialogue option).