When you're done, take the body that Mindy asked you to bring to her, and get onto the roof. In the safe, there will be, apart from the rune, ivory and three silver ingots together worth 225 coins.

You can also check the engraving on the gold plates in the prayer room. The first one is lying near the safe the second can be found on the table in the room where the two overseers were. In order to unlock it, you have to find the combination written down in two books. On the desk, there's a blueprint - Fire Hardening Treatment, next to the desk - a painting - The Vice Overseer's Predicate Logic (200 coins), and in the safe in the neighboring room - a rune.

After neutralizing all opponents here, you can stand up. He's sitting at his desk in the room on the left. One more Overseer can be found on this floor. The other one will enter a room on the right to pray. One of them will stay in the room you can use blink to get behind him and eliminate the threat. Inside the room, you will find two guards talking - wait until they finish and get separated. After neutralizing the guard use blink to get to the balcony pictured above.

Dishonored 2 mission 7 safe