Turk and Rooster are two aging NYPD detectives who have been partners for 30 years. They are faced with a serial killer who is murdering other sociopathic criminals. They both have personal issues. They start working with Perez and Riley, a younger team. Tensions between the pairs of partners is inevitable, especially since Turk is now living with Perez's ex-girlfriend. She also happens to be a homicide detective. But before Turk and Rooster can retire, they are called in to investigate the murder of a notorious pimp, which has ties to a case they solved years before.