Alex joins his father on a business trip to Amsterdam.
During the day he hangs out with the daughter of a family friend.
They visit the usual sights but also coffee shops and flea markets off the beaten track.
At one of these markets Alex spots an ancient-looking mask.
Before he knows what he's doing he buys it. Later, in his hotel room, he feels compelled to put the mask on.
Alex is sucked into a parallel Amsterdam, one from centuries before which begins to reveal the dark past of both the building he is staying in and the little girl who once lived there . . . edging stealthily towards the terrible twist.