Mask Hysteria

Mask Hysteria is an overseer quest and part of the Mystery of Vault 31 multi-stage questline in Fallout Shelter.

Walkthrough
In the building, which has a random layout, there are several groups of feral ghouls that the dwellers must fight. They are in groups of two to four and may also include an irradiated ghoul. The target ghouls are found near the top of the level. The first and third dialogue options avoid the fight, while the second and fourth options end in combat. The ghost costumes can be retrieved from here.