Flack was born and raised in Queens (episode 9.03 "2,918 Miles"). As a child he would sometimes play in a hedge maze at the Queens Botanical Garden, where he later investigates the death of a Chelsea University student, though he says that by that time he hadn't been there in years (episode 3.15, "Some Buried Bones"). His family, besides his "legendary" father, includes a sister named and at least one brother. His mother used to make corned beef every Wednesday, and Flack claims that he would "endure every one of brother's insults for one more taste of that paradise" (episode 4.04, "Time's Up"). As children, he and Samantha were the best of friends. They would often share an old Walkman on car trips, much to their father's disapproval, and listen to their favorite song, "Red Rain" by Peter Gabriel (episode 5.07, "Dead Inside").