An Infernal Puzzle Box has come into the hands of the party, delivered by one of Elturel's Hellriders before he met his untimely end. The minions of Zariel will stop at nothing to reclaim the puzzle box, and the adventurers have come to realize that one of them may not be all that they seem - the puzzle box has gone missing, and time is of the essence! Who has been slain and replaced by a devil in disguise, what was the murder weapon, and where has the puzzle box been hidden?