Kieran Hart has just gone through a divorce and is starting over with a new job at a DNA discovery site. After finding out she's adopted years earlier, she sends in her sample, hoping to find her birth parents, and instead, finds herself in a police station, being accused of a crime she didn't commit because her DNA was a match to a homicide. Only, it's not Kieran's DNA. It's her identical twin sister's DNA. The sister she never knew she had.

Carina Whitlock is the top ADA in her office and is on her way to becoming the next district attorney when she is handed the case of Marin May, Kieran's twin sister. It seems like a fairly open-and-shut case until she spends time with Kieran and finds herself not only believing that Marin might not have committed the crime, but also that Kieran might be more than someone she's supposed to know through a case.

All the evidence points to Marin being the killer and maybe much more than just that, but Kieran can't stop trying to help her sister and becoming friends and maybe more with the ADA assigned to prosecute the case.