"In Honor of Our Fathers"; - "Wisdom of the Earth" [Campaign 3, Mission 4]

Here, the action with the demon occurs, and before that, there's BlockGame – a function that blocks the game. Since the script is failing, the UnblockGame() function doesn't trigger, and the game doesn't unblock. Try entering @UnblockGame() in the console – then the game will continue, and you can see if that demon is even there.