A forgotten mansion in the old quarter of Magnapolis conceals a terrible secret. Held captive in the mansion is an evil phantom known as ‘The Sorcerer’, waiting until some unfortunate frees him and becomes the first victim of his horrendous powers. It has to be the perfect place for Alan and his friends to hold a Halloween party! When the party is under way, Alan seizes the opportunity to become invisible from time to time and play a few tricks on his friends. Inadvertently, he somehow manages to set free the hideous phantom. The Sorcerer loses no time in attacking first Alan and his friends, and then the whole city. Whether visible or invisible, there seems to be no way that Alan alone can capture and lock up the sinister spectre again. He and his friends need to work as a team to confront the phantom and solve the enigma which will enable them to catch him. Naturally, the dark secret of the mansion seems impossible to uncover, and more invisible than the Invisible Man himself