Beth Stone (Kim Director) is the villainess from Elementary episode 5.03: "Render, and then Seize Her" (airdate October 23, 2016).
The beginning of the episode shows Beth Stone, a news reporter, as a kidnap victim, while Kenneth Tolan was murdered from outside the house where Beth was held captive. Beth was finally rescued later in the episode, and in her interview with police, she stated that she was kidnapped by a pair of Pakistani men, who tied her wrists to a stake. However, at the episode's climax, it was revealed that Beth staged her own kidnapping, and her villainous motive was to gain half of her husband's fortune after she divorces him.
Beth and her husband, Aaron, were married for a decade, but as revealed later on, a special prenuptial agreement was signed that only allowed Beth to receive 5% of Aaron's fortune in a divorce settlement. However, if the marriage lasted long enough, Beth could receive half, and with that in mind, the evil Beth devised a plan to delay Aaron long enough to increase her settlement. She collaborated with Dennis Karig to stage her kidnapping, and it was Karig who killed Tolan to keep him from ruining their plan. As for the marks on Beth's arms, they were self-inflicted, and her false story regarding Pakistiani men kidnapping her was racially motivated. It was assumed that Beth was arrested for the fake kidnapping scheme and for her complicitness in Tolan's murder.