Dope by Sara Gran

Set in 1950s New York City, the story follows Josephine Flannigan, a former heroin addict turned private investigator, as she is hired to find a missing girl named Nadine. As Josephine delves deeper into the city's gritty underworld, she confronts her own past and struggles with the temptations of her former life. The investigation leads her through a maze of deception, addiction, and betrayal, ultimately forcing her to face the harsh realities of the choices she's made and the world she inhabits.