Plaza with bins: Enter the plaza with bins. Sylvie says to build steps to get to the roof of the outhouse.

There is a trash bin at right and a crate at left that are movable. They can be pushed or pulled.

Sylvie can only walk one square at a time.

Move the trash bin at right to be in front of the big garbage bin at top right.

Move the crate to be in front of the round trash bin.

Climb up.

Clean the mantel-ledge and fireplace: This part is very dark. You might need to raise the brightness of your computer and/or untick the shadows options at main menu.

Look close at the mantel of the fireplace and see 9 tiles-buttons with designs on them.

In inventory combine bough with moist napkin to get napkins on a bough.

Take the thread hanging from the protective cover of the furniture at foreground left. Use the thread on napkins on a bough.

Use the napkins tied with a thread to a bough on the middle dirtiest tile button.

Look down inside the fireplace. Take the small shovel.

Use broom on the soot of the fireplace and see 6 of the tiles similar to the ones on the mantel of the fireplace.

Use the small shovel (broom can also be used) and press the buttons in the order shown by the tiles inside the fireplace below.

From left to right, press the tiles in positions: 7 4 9 6 2 5.

Immediately, click the small shovel on the opening to the secret passage to stop it from closing.