Escape from the Dungeon

Nienburg in the deepest Middle Ages... shackles are put around your ankles, only a little light penetrates into the dungeon. Just before the dungeon master shuts the door, you hear him say with a sneering smile: "The executioner will be here in an hour...". What happened? Why is your community locked in the dungeon? Free yourselves from the shackles, solve the mystery of your captivity, and find a way out to freedom before the executioner arrives!