In "The Coldest Case," homicide detective Billy Harney sends his new partner, Kate, deep undercover to infiltrate a notorious Chicago drug ring. When several members of the ring turn up dead, Billy abruptly pulls Kate out, blowing her cover. Kate's informant inside the gang disappears - along with the ring's black book. As Billy and Kate investigate the ring's murders, they'll be pulled into a dangerous web of corrupt politicians, vengeful billionaires, drugged pro-athletes, and violent, dark web conspiracies, all in search of the missing black book.
