First you should talk to caretaker (several times). You'll arrive at leader's place. Talk with her and learn about ghoul people. Switch to Seeker and have a chat with leader.

Spill mountains MAP

1. Quinn's sickbed
2. Storage room
3. Elevator
4. Tanning Room
5. Leader
6. Living room 1
7. Living room 2
8. Helium machine
9. Ballon
10. Platform
11. Hall of Records
Switch to Quinn, walk to tanning room and try to get a tank. Oops. Lead Seeker to Storage room and let him lower the rock. Grab alcohol from shelf. Back to Quinn and grab revealed canister. Go to helium machine and fill canister with helium. Stride towards balloon and wait there.

Send Seeker to tanning room and grab breathing mask. Visit bouth Living rooms and steal all lamps and gunpowder bag as well. Walk to the helium machine and get transparent lid. Go to the top (Hall of records) and use rope to descent into gulf (Seeker can also swing across if he wants to). Drop lamp and cover it with a lid. Yup, grab the key and go to the elevator.