You're trapped in a locked-room mystery where the culprit might be a witch, might be impossible, might be you're watching it wrong entirely. Every answer the show gives you is a trap designed to make you doubt the previous answer. By episode 13 it stops pretending to be a mystery and becomes something closer to psychological warfare, where the real puzzle isn't who killed the family, but whether any of this actually happened at all.

The Ushiromiya family arrives on isolated Rokkenjima for their yearly gathering, where each relative's finances are usually discussed. This time, patriarch Kinzo's failing health puts his inheritance on the table. Kinzo has other concerns. Told by his longtime friend and physician that his end is near, he longs to see his true love, the Golden Witch Beatrice, once more, and after years steeped in black magic he begins a ceremony to bring her back. Then a typhoon cuts the island off, and a series of mysterious murders begins. The eighteen people trapped there must fight to survive in a horror mystery where the line between fantasy and reality grows uncertain. The real puzzle is not only who is killing whom, but whether anything can be trusted when supernatural forces may actually exist.