After mingling with a few zany characters and watching this long-running show, which takes about an hour and contains at least one murder, you confer over dinner with your tablemates, grill the suspects, and, if you feel confident, accuse a killer. The cases (there are between five and a dozen in the repertoire, depending on the cast) change nightly, so you can attend several times without duplicating the riddle. Actors seem to be having fun, and they’ll tone down the grown-up jokes if they see kids in the crowd. Kids love participating in the detective Q-and-A segments. Audiences appear to be grateful for a rare chance to employ their brains in this town. Lots of brochures offer discount rates.