At the end of this month, Mohonk Mountain House, a grand Hudson Valley lodge founded in 1869, will hold its fiftieth annual Mystery Weekend, in which guests gather for a few days of sleuthing around the property, examining staged rooms and interviewing actors playing characters, in an attempt to solve a fictional crime. The event has a storied history among mystery buffs; some of its first scripts were written by the celebrated author Donald E. Westlake, along with his wife Abby, and they often collaborated with notable writer friends, including Stephen King, Edward Gorey, and Isaac Asimov, on everything from performing to graphic design. A half century ago, few, if any, hotels offered “immersive theatre” as an amenity, and the Mystery Weekend became a hot ticket for city dwellers—the first weekend, in 1977, drew more than two hundred participants. Soon, mystery-solving events were de rigueur at many rural hotels, whose owners found that staging crime scenes was a surefire way to lure cosmopolitans to the country during the off-season. In 1992, the Times reporter Alessandra Stanley noted that the swelling glut of mystery parties came in three categories: serious, “in which participants form teams and spend two to three days”; semi-serious, which “take place in large hotels, over meals, and are meant to be more entertaining than challenging”; and those on cruise ships, which are fully unserious. (Many people on cruises, an expert clucked to Stanley, “have never even read a mystery.”)