The city of Chicago is relentless. Murders and other violent crimes pile up: a woman lies in the hospital in a coma, a man is brutally attacked in his sleep, and a child suffers.

Detective Maria Mateo is new to the Chicago Police Department, but she's not soft. In spite of her strength, every case that arises brings troubling memories of her past and fear that her deepest secret will be revealed and threaten everything she's worked for.

When her captain discovers she's having difficulty with her health, she faces the possibility of losing her badge for good. Mateo struggles to keep her personal baggage out of her work, but when a woman is almost smothered, the investigation leads Mateo to help someone she never thought she'd see again.