The series revolves around the Reagan family of police officers with the New York City Police Department. The widower, Frank Reagan is the New York Police Commissioner. Before joining the NYPD he was a Marine during the Vietnam War. His son Danny is a top NYPD detective. He is also a former Marine of the Iraq War. Linda Reagan is Danny's supportive wife. Erin Reagan-Boyle is Frank's daughter who is an Assistant District Attorney and single mother, prosecutes many of the criminals Danny arrests. Nicki Reagan-Boyle is Erin's daughter. Jamie Reagan is Frank's youngest child, who is a rookie police officer and recent Harvard Law graduate. Henry Reagan is Frank's father and grandfather of Danny, Erin and Jamie who is a former NYPD police commissioner, now retired. He was a Marine in the Korean War.