Jack Donovan boasts about his marvelous turquoise ring during a dinner party. The lights are turned out in order to test the truth of Jack's assertion. A moment later Jack is found lying on the table dead, a game knife stuck into him. The ring was supposed to exert a baleful influence over women, and several of those present had good reason to want the ring done away with, as well as its owner. Who could guess the murderer? This fascinating problem is offerered to the audience.