From the release:
Evil threatens Arkham from within with the approach of the Twilight Fair. The organization behind the festival, the powerful Order of the Silver Twilight, controls the city from the shadows, using their money and influence to forge alliances, lobby politicians, and conduct strange rituals behind closed doors. Those who seek out the truth of their operations often find themselves disgraced, arrested, or simply disappearing altogether. What is the Order trying to hide?
The Sanctum of Twilight expansion for Mansions of Madness is on sale now at your local retailer or online through our website!