The Diamond Pin is a classic locked room mystery with few clues and no end of suspicion. Mrs. Pell is having a Sunday dinner with the local minister, the minister's wife and Iris, one of her two young relatives she intends leaving her wealth to, but who she treats quite viscously. During the dinner she pulls the trick on Iris who ends up with black ink all over her face and dress. After dinner, Mrs. Pell goes into her private room. Soon, a servant hears her scream. Carolyn Wells (1862-1942) was an American writer and poet. Among the most famous of her mystery novels were the Fleming Stone Detective Stories, and Pennington Wise series. She also wrote several Sherlock Holmes stories.