Straight laced and Up tight, FBI Special Agent Sarah Ashburn is a detective with a reputation for excellence--and hyper-arrogance. Shannon Mullins, one of Boston P.D.'s"finest," is both foul-mouthed plus it has a very short fuse, also uses her gut instinct and street smarts to capture the many elusive criminals. Neither has had even perhaps a friend for that matter, or even somebody. They eventually become the final thing anybody Buddies when these two wildly incompatible law enforcement combine forces to bring down a drug lord.