Millicent Lee is a young bride whose faith in her husband is tested when she finds a book in his possession entitled "How to Be Happy, Though Married", along with a photograph of a beautiful young woman.

Stanley Montjoy and his brother Jim journey to examine their mining property in South America, where a dark-eyed beauty named Diana Ramon assists them in their financial dealings. Stanley returns to the United States to marry his sweetheart, Millicent Lee, while Jim lingers on with Diana. As a joke, Bob Davis gives Stanley and Millicent a cynical treatise on marriage entitled "How to Be Happy Though Married," which poisons the young bride's thoughts with doubts about her husband's past. Her suspicions turn to rage when she discovers a photograph of Diana in Stanley's trunk. Jim and Diana wire Stanley that they have married and are returning home, but when Stanley meets them at the station, Jim becomes lost in the crowd. Diana, dropped at the house to await Jim and Stanley, shocks Millicent by her presence, and although neither can speak the other's language, a furious battle ensues. When the husbands return home, the situation is explained and the two women become friends.—Pamela Short