How our reliance on Child Protective Services makes motherhood precarious for those already marginalizedIt's the knock on the door that many mothers fear: a visit from Child Protective Services (CPS), the state agency with the power to take their children away. Over the last half-century, these encounters have become an all-too-common way of trying to address family poverty and adversity. One in three children nationwide-and half of Black children-now encounter CPS during childhood.In Investigating Families, Kelley Fong provides an unprecedented look at the inner workings of CPS and the experiences of families pulled into its orbit. Drawing on firsthand observations of CPS investigations and hundreds of interviews with those involved, Fong traces the implications of invoking CPS as a "first responder" to family misfortune and hardship. She shows how relying on CPS-an entity fundamentally oriented around parental wrongdoing and empowered to separate families-organizes the response to adversity around surveilling, assessing, and correcting marginalized mothers. The agency's far-reaching investigative apparatus undermines mothers' sense of security and shapes how they marshal resources for their families, reinforcing existing inequalities. And even before CPS comes knocking, mothers feel vulnerable to a system that jeopardizes their parenthood. Countering the usual narratives of punitive villains and hapless victims, Fong's unique, behind-the-scenes account tells a revealing story of how we try to protect children by threatening mothers-and points the way to a more productive path for families facing adversity.