for target practice in Season 4 and re-certification training in Season 5, Frank never fires his gun during the course of the series. It is implied on a few occasions that he is in fact unwilling to use deadly force, which becomes significant during the two-part finale of Season 6. The stroke In the fourth season finale, Frank suffers a stroke while interrogating a suspect, and nearly dies. When he returns to duty, his speech and memory have been noticeably impaired. He is assigned desk duty until he passes his firearms exam, and is frustrated when others baby him. 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. The effects of Pembleton's stroke rapidly diminish over the course of the fifth season, mostly due to pressure from NBC who felt that Pembleton's halting delivery and memory lapses made his character difficult to watch. By the middle of the season, only a slight occasional stammer remains; by sixth season, the effects of Pembleton's stroke seem to have been almost magically eradicated. 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. Also, in the two-part finale of Season 6, he seems to struggle to aim his weapon and appears unable to see clearly, switching from one eye to the other. His determination to overcome his stroke and return to police work also alienate him from Mary and their daughter Olivia, and they leave him for a time. Pembleton and Bayliss When Det. Tim Bayliss is assigned to the homicide unit, Lieutenant Giardello partnered him with Pembleton, who had no patience for a rookie. They were partners for most of the series, though Frank never allowed Tim to get too close. Although Bayliss had great respect for Frank, to the point of calling Frank his best friend, Pembleton was often dismissive of Bayliss' attempts at friendship. 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