The 7th Guest

An unidentified man finds himself in the foyer of an old mansion that was once the property of a well known toy maker, a Mr. Stauf. As the man explores the mansion, he discovers that the mansion is haunted by six ghosts of people Stauf had called together for a party, with the expectation that an unknown seventh guest would eventually join them. After further exploration, it's discovered that the six guests have been caught in an elaborate trap; as they solved the mansion's puzzles and uncovered the mystery themselves, each was killed one by one, as Stauf's true nature as a man in league with the devil is revealed. However, as the six guests and the protagonist witnessing these ghostly events wander the mansion, they all have one question on their minds. Who is the seventh guest?