Use the following combinations at the indicated lock.

Forest Hut: 2-4-3-1 (four buttons, two on each side of the second story fireplace)
Catacombs: 4-1-3-2 (four stones on either side of the iron bars)
Chimney: 3-2-4-1 (valve by the stairs in the Arsenal District)
"Victor's Secret" quest: 1-4-3-1 (books in the bottom floor of the library in The Net of the Mask building)