Eleven-year-old Flavia de Luce, an aspiring chemist with a passion for poison, is propelled into a mystery when a man is found murdered on the grounds of her family's decaying English mansion and Flavia's father becomes the main suspect.

Ree Dolly's father has skipped bail on charges that he ran a crystal meth lab, and the Dollys will lose their house if he doesn't show up for his next court date. With two young brothers depending on her, 16-year-old Ree knows she has to bring her father back, dead or alive.

NYPD detective Jacob Kanon and Swedish reporter Dessie Larsson traverse Europe in hot pursuit of a serial killer, one who sends a postcard before each murder and was responsible for the slayings of Jacob's daughter and her boyfriend.