A group of friends decide to spend a weekend in a castle belonging to Riccardo, a moody and hyper-sensitive young artist. The only other inhabitants of the castle are a mysterious housekeeper, Caterina, and the demented Aldo. The group are joined by two friends: Serena and a young American medium, Anthony. During a seance Anthony predicts a tragedy, then leaves the castle, shocked by his own visions. An hour later, Serena is found strangled to death in bed. The others become gradually more and more diffident and suspicious, especially when another girl is murdered...