On your adventure in The Mortuga Submarine to uncover the secrets of a mysterious murder in The Mermaid Mask, you'll eventually find your way to the Child's Room, where you'll be faced with the second major puzzle of the game.
You can start the puzzle by interacting with the chest in the bottom-left corner of the room, where you're faced with six cards and four glass lenses and asked to put them in the correct arrangement with only a phrase as your clue to the solution.
Cards and Glass Lenses Puzzle Solution for The Mermaid Mask
The one hint you will get for solving the card and glass lens puzzle in The Mermaid Mask is hidden underneath the cards. It says: Jennifer and Margaret gaze jealously at Patricia, whose doll is neither too large nor too small.
To solve the puzzle, you need to place the three cards with the faces in a row side by side, with the three dolls underneath each. You can then use the glass lenses to make the two girls on the left and right stare at the one in the center, and then use the rest of the lenses to make the doll on the left large and the doll on the right small. The doll in the middle can remain without a lens.
You can see the full solution of the puzzle in the image above!