Dark Hearts is the thirteenth episode of Season 7, airing on October 11, 2013.
In 2008, when ballroom dance teacher Miriam Helmick's business prospects fail, she begins forging checks to steal money from her husband, Alan. When Alan begins to suspect her, Miriam shoots him in the head, and receives a life sentence for the murder plus 108 years for fraud. She is also suspected of murdering her first husband five years earlier. In the early 1920s, Clara Carl is a farmer's daughter with dreams of wealth and prestige, and her greed leads her to poison two husbands and her father-in-law with arsenic for their inheritance money. Sentenced to life, she cons her way into parole after only 15 years behind bars. Damaged from a life of tragedy and suffering from borderline personality disorder, Carol Kemp falls head-over-heels in love with online crush Martin Rusling, but he doesn't reciprocate. After Martin rejects Carol's offer to make their relationship more permanent, Carol flies into a rage and stabs him once in the heart. A remorseful Carol is sentenced to life with a minimum of 13 years.