Found Laser Pistol

Examine the BUG COLLECTION on the side of the wall.

Examine the bookshelf to trigger a puzzle.

Bookcase Puzzle: Highlight the books with the right analog stick, then use the left analog stick to slide all books to the left. This reveals a yellow switch on the right side of the shelf.

Press the switch to make the bookshelf open, revealing a hidden room.

Take the ++MAP OF OUR HOUSE++ from the wooden shelf inside the hidden room.

The door on the side of this room is locked, so exit the room and step back into the hall.

Walk to the door that swung shut earlier at the end of the hall. It is locked, so you must go back downstairs.

A cutscene will trigger as Alex moves down the stairs. Alex will receive the ++OLD REVOLVER++ after this cutscene (check your inventory).

Objective Update: Investigate the basement.

Move down the stairs into the basement. The basement is flooded.

A cutscene will play once Alex steps into the water.

A Lurker will attack immediately after the cutscene.

Combat Strategy vs. Lurker: Run to the Lurker's side, let it lunge and miss, then run up and attack while it recovers. Alternatively, use an A, A, A, X combo.

Defeat the Lurker to unlock the 'Lurk No More' (10G) achievement.