Which tactic does the Society use to gather information about Mr. Curtain?

The tactic used by the Society to gather information about Mr. Curtain is to impersonate students and staff at the Learning Institute. This method allows them to observe Mr. Curtain's actions and gather information without drawing attention to their true identities. By blending in with the environment, they can eavesdrop on conversations, participate in lessons, and gain insights directly related to Mr. Curtain's plans and operations at the Institute. This approach is subtle and effective, enabling them to collect valuable intelligence while remaining inconspicuous. The other strategies suggested, such as planting a spy, hacking, or bribing staff, imply a more overt and risky method which would likely attract immediate scrutiny and could jeopardize their mission.