This line of dialogue serves as a fitting summary for “Brigadoon,” a classic written during the Golden Age of musical theater that is now being staged at Porthouse Theatre. After getting lost in the mist, the two friends stumble upon Brigadoon, a village that appears for only one day every 100 years. The show opened on Broadway in 1947, propelling Alan Jay Lerner and Frederick Loewe–two classic icons of musical theater–into prominence. The “miracle” that protects the village of Brigadoon from the outside world lacks logic. “Brigadoon” runs through August 9 at Porthouse Theatre, 3143 O’Neil Rd., Cuyahoga Falls.