A calculating killer who calls himself The Teacher is taking on New York City, killing the powerful and the arrogant. Discovering a secret pattern to The Teacher's lessons, Detective Mike Bennett realizes he has just hours to save New York from the greatest disaster in history.

Detective Harry Bosch investigates a cold case and the murder of a city councilman's son. The cases are unrelated but they twist around each other like the double helix of a DNA strand. One leads to the discovery of a killer operating in the city for as many as three decades; the other to a deep political conspiracy that reached back into the dark history of the police department.