As you fight your way through the sewers your main objective is going to become pretty clear. You need to open the U-Shaped Door to try and rescue Ada/Sherry (depending on whether you’re playing Leon or Claire’s campaign. The problem that you’re going to encounter is that there are six electrical boxes that are in your way and you’re going to need to track down three chess pieces to complete this puzzle.
The pieces that you’re going to need to find are the King, Queen, and Rook. You’re going to have to navigate through some dangerous environments in the Sewer to find them. There will be new enemy types as well as some that you’ve already seen. More so than the Police Station the Sewers can be dangerous if just for how confusing the area can be.
First things first we’ll go after the easier items to find and that’s the Rook piece. The Rook piece will likely be found before you even know that you need it as you’ll come across it in a box that controls a bridge in the Upper Level of the Sewers. The map below shows the location of the Rook. Unfortunately, you cannot take the Rook at this point as removing the piece will cause the bridge to raise and you need to cross to progress. You’ll be able to come back to this spot once you’ve created a shortcut that doesn’t involve taking the bridge that the Rook piece controls.
Rook Plug Piece Location
What you’ll need to find to actually set things in motion and open up some different pathways is the T-bar piece. This is located near the cable car on the north side of the Treatment Pool in the middle section of the Sewer. This item is a red bar that can open locked door all throughout the sewers and in the Underground Facility. Once you have the T-bar in hand you will be able to open up the shortcut that allows you to complete this puzzle.
The T-bar that you’ve found will actually give you access to the Bottom Waterway which is where you’ll pick up both the King and the Queen Plug Pieces that you need to complete the puzzle and rescue Ada. Once you’ve reached the Bottom Waterway you’re going to want to navigate these waters very carefully as a new powerful enemy waits below the surface that can poison you. You’re trying to make it to the Supplies Storage Room that is located on the far West Side of the Lower Level of the Sewers.
Once in the Supplies Storage Room you can check out the video below on how to get both the Queen and King plus as well as a powerful new flamethrower weapon. At this point you should have the Queen and the King piece, now you just need the Rook piece and you can head back to the puzzle area where you’ll need to put the plugs in their places.
Now that you have these pieces and the T-bar in your inventory you can open the door to the Bottom Lift which will bring your right to the Rook piece. Now that you have the Rook piece it’s just about opening up doors that will lead you back to the plug puzzle.
Once you make it back to the puzzle area you can use the diagram below for either Scenario A or Scenario B to put the pieces in the right order.