He met his future wife, Mary, on the Great Lawn in Central Park shortly after graduating from the police academy when he was 24.

At the same time, he often fails to endear himself to his fellow detectives, who resent his black-and-white attitude toward the job and his arrogant demeanor.

The thought that God can allow such crimes to be committed greatly disturbs Frank, and he chooses to renounce his faith, refusing even to go to church until near the end of Season 5.

In Season 3, Pembleton is asked by Deputy Commissioner James C. Harris to help Congressman Jeremy Wade cover up a homosexual liaison by dismissing a report that he was kidnapped.

Pembleton is later called to testify about the cover-up and reluctantly states that he decided to offer Wade the deal on his own; however, he continues to harbor a deep resentment for Harris long after the incident is closed.

When his blood pressure medication impairs his focus and sexual relations with Mary, he briefly stops taking it, but resumes after failing his first attempt at the exam.

However, the stroke adversely affects his effectiveness when he refuses to take his medication for a time; in the episode "Kaddish", he aggressively questions a suspect he believes to be guilty of a shooting in a fast food restaurant, only to be told that another person has confessed to the crime.

His determination to overcome his stroke and return to police work also alienates him from Mary and their daughter Olivia, and they leave him for a time.

Tim Bayliss is assigned to the homicide unit, Lieutenant Giardello partnered him with Pembleton, who had no patience for a rookie.

When Bayliss expresses sadness at Frank's abrupt resignation in Season 3, Pembleton is indifferent, although he willingly partners with him again after coming back to the force.

Their partnership was strained when Pembleton investigated the accidental shooting of a foreign exchange student by Tim's cousin, Jim (portrayed by David Morse).

In the Season 5 episode "Betrayal," a case involving a man beating his stepdaughter to death causes an emotional Bayliss to tell Frank about how his uncle sexually abused him as a child, and his father was dismissive when told about it.

In the Season 6 finale, during a gun battle with members of dead drug kingpin Luther Mahoney's organization, Frank takes aim at a suspect but cannot bring himself to fire.

Disgusted by Giardello allowing Kellerman to resign without charges and tormented by guilt over Bayliss's shooting, Frank quits the force and is absent for Season 7.