Sarah Longson is a one-shot villainess from Monk, appearing in Season Seven's "Mr. Monk on Wheels."
She was played by Pamela Adlon.
Sarah Longson is the personal assistant to biotech CEO and fellow scientist Dean Berry, but she was secretly planning to steal Berry's experiment, a batch of genetically altered cornseeds, and sell them to a group in China. As part of her evil plan, Sarah gave Berry a bicycle as a gift, which contained a special eight-digit keypad lock, which was a key piece of her plan. She had petty criminal John Kuramoto steal the bike and get her the code, and as Sarah figured, the code for the lock was the same as the code for the safe that the seeds were in; as Berry never bothered to use a different code. Once she downloaded the code, Sarah took the seeds and replaced them with a batch of ordinary seeds.
Sarah's alliance with Kuramoto was revealed when she met him at a cemetery and paid him off. At that moment, however, Sarah shot and killed Kuramoto, and regained the money she paid him. When confronted by Adrian Monk, Sarah correctly stated that he had no proof that she took the seeds, but he did have proof that she killed Kuramoto. The tire tracks left on the cemetery were from Sarah's eco-friendly sandals. Knowing that she was cornered, Sarah tossed a batch of liquid fertilizer in Berry's eyes and attempted to escape. Sarah pulled out her gun (the same one she used to kill Kuramoto) and attempted to fire at Natalie, only for Natalie to snatch the weapon away and hold her at gunpoint.