There are a total of 5 Runes that can be collected in this mission.
#1) This one is located inside of Galvani's Offices in the second area of the Distillery District, inside the secret lab where you found the rat poison item for Granny Rags side mission in High Overseer Campbell. You need to pull a certain book on the bookshelf in order for it to open, and the Rune will be right there.
#2) This Rune is located inside of the Art Dealer's Apartment, inside the safe. In order to get the combination for it, you need to be on the second side mission for Slackjaw within the overall mission. The Art Dealer is inside of the Golden Cat Bathhouse, and you need to keep electrocuting him until you can get the combination from him. Note that this combination seems to change on each playthrough, so it may vary.
#3) There are three Runes located in the Golden Cat area. The first one is in a building located just to the right of the stairs leading up to the main entrance. The Rune is on the second floor, on a table.
#4) This Rune is located on the second floor of the bathhouse. At the top of the stairs, with your back to them, go to the right and through the double doors. The Rune is hanging above the table on the wall.
#5) This last Rune in The Golden Cat is located on the top floor. It's in the room with the Courtesan, next to where Emily is being held.
