I am an Dungeon Master. I would lead game about you are several of your known persons (up to 7 people) locked with you in one place like tavern, space station, train, school class etc. One of them are not who he looks - actually he or she is impersonator (alien, criminal, spy etc) wearing realistic rubber skinsuit of your known person to hide his real nature from others. Impersonator tries to hide his real nature from others. You need to diacover who it is until it's too late.