Vying to become Boston's next DA, Decourcy takes on a murky case involving a murdered police officer. He recruits the help of Caysen, who is becoming increasingly alienated from the officers in his unit. As the Drydens try to solve their Victoria problem, the Rohrs drop Benedetta off for her freshman year at NYU. They return empty nesters but to no peace and quiet. When Siobhan receives a distressing phone call, a dark secret resurfaces.