Donna Kaplan (Molly Price) is the main villainess from "The Rat Race," episode 1.04 of Elementary (airdate October 25, 2012). She is a secretary for Chief Investment Officer Jim Fowkes, who called Sherlock and Joan regarding the disappearance of their COO, Peter Talbott. As revealed later on, Donna is also a serial killer, having killed not only Talbott, but their previous COO,Gary Barnes, and many others.
Donna used Barnes' and Talbott's peanut allergies against them, as she poured peanut oil in each of their meals to kill them. Her motive was to get Fowkes promoted, which would increase her pay and give her pension rights, among other things. Sherlock confronted Donna regarding her role as they walked to her car, but unfortunately for Sherlock, this was exactly what the evil secretary counted on: Sherlock following her to an empty parking garage, which is where she tased Sherlock and placed him in the back of her car.
After Sherlock came to, Donna revealed her latest plan; kill Sherlock and bury his body on Fowkes' property, which would get him arrested and open the door for her to become Daniel Cho's secretary. When Joan attempted to call Sherlock, Donna posed as Sherlock and sent a text to Joan stating that everything was fine, and later forced him to dig his own grave. At that moment, Sherlock had broken free from his capture and used Donna's own taser against her. It was Donna's text that would be her undoing, as Joan noticed that it wasn't in Sherlock's usual style. Knowing that Sherlock was in trouble, Joan had police sent to Donna and Sherlock's location, resulting in Donna's arrest.
- Molly Price went on to portray evil parole officer Donna Marshall in Law & Order: SVU.