At Marcus's behest, Carl and the Department Q gang—Rose, Assad, and Gordon—reluctantly begin to investigate. However, they quickly discover that Marcus is on to something: Every two years for the past three decades, there have been unusual, impeccably timed deaths with connections between them that cannot be ignored. As they dig deeper, it becomes clear that these "accidents" are in fact murders by a very cunning and violent serial killer.
Faced with their toughest case yet, made only more difficult by COVID-19 restrictions and the challenges of their own personal lives, the Department Q team must race to find the culprit before the next murder is committed, as it is becoming increasingly clear that the killer is far from finished.