I am no ordinary ajumma. I am a killer. Recently widowed and unemployed, Mrs Shim and her two children face an empty fridge. As her job options run out, she answers an ad for the Smile Detective Agency. Within weeks, she has turned it around. For Mrs Shim is sharp as a blade, handles business cleanly and is like a padlock when it comes to keeping secrets. By day, she prepares kimchi for her family and her neighbour with dementia; by night Mrs Shim is out on a contract. But what starts as a need for survival escalates into a thirst for vengeance. For Mrs. Shim is done with being everyone's doormat. Diving headfirst into her new career among petty criminals, ghosts and assassins, Mrs Shim's past soon comes hurtling towards her.