Carnival of Synn

From the introduction:

The adventurers are traveling The Long Road, between Triboar and Longsaddle, when they come across the campsite of a traveling carnival. The carnival-master is a beautiful and seductive tiefling named Synn. She asks the travelers to stay for dinner and watch the show. It is a new play called The Beast of Barovia. The entertainment is amazing and wonderful… up until the point that the act turns real. Suddenly, the party finds themselves immersed in a nightmare, fighting for their lives against horrifying creatures. Even if the protagonists survive, the unfortunate souls could be forever trapped in the cursed realm of Ravenloft.