A Boston police officer goes to Nantucket to investigate the murder of his partner, but he finds more than he bargained for.

A matriarch of a dysfunctional family is pushed to her tipping point by the disappearance of her son.

In the aftermath of an unspeakable act of terror, Police Sergeant Tommy Saunders joins courageous survivors, first responders and investigators in a race against the clock to hunt down the Boston Marathon bombers before they strike again.

Uptight and straight-laced, FBI Special Agent Sarah Ashburn is a methodical investigator with a reputation for excellence--and hyper-arrogance. Shannon Mullins, one of Boston P.D.'s "finest," is foul-mouthed and has a very short fuse, and uses her gut instinct and street smarts to catch the most elusive criminals. Neither has ever had a partner, or a friend for that matter. When these two wildly incompatible law officers join forces to bring down a ruthless drug lord, they become the last thing anyone expected: buddies.