Like the itch on his ankle, which opens and closes the film, the killing of the little girl is something that Black finds continuously nagging. He's an angler, promised a trip to land the catch of a lifetime in Mexico by his colleagues, a man at the very end of his working life. He promises on his "soul's salvation" to find the Larsen child's killer. The result is suggestive of a 'fisher of men', Black waiting for the right catch, whether marlin or murderer. Perhaps the presumably twice-married, now separated detective feels that his remaining life needs commitment and a purpose. His motives for taking his last case, and investing so much in his dogged pursuit of the truth, are otherwise unclear. Whatever the reasons, his sincerity pledged to the victim's mother, that troth sworn on the dead girl's straw crucifix, makes Black's investigative obsession suggestive of a religious quest - as does the grandmother's tearful story of the angels, and his own straight-faced confirmation to the mother that "there are such devils." Add the birds wheeling around Black's head as he stumbles and drinks, his blundering into the church service held by the suspect Jackson, the child at the picnic ground singing 'The Bible tells me so' and so on, mean clear spiritual parallels are at work. Of course the final, shocking scene, which leaves the ravaged detective mouthing his convictions to the air is a bleak one. It suggests of a loss of faith, if not in God, certainly in himself. But, if we recall the Christian philosophy of good works done in secret, with no hope of earthly reward, the conclusion is less bleak. Black is unaware of his 'success' and has sacrificed his last chance at mortal happiness. Like God, the viewer at least is privileged to know the truth.
As Black's belated chief suspect, Jackson's appearance unfortunately telegraphs likely guilt to any cine literate audience. The actor Tom Noonan, playing Jackson, has had several villainous parts in his career. He earlier played the demented killer Francis Dollarhyde in Mann's frightening Manhunter (1986), as well as the parody villain in McTiernan's Last Action Hero (1993). Only because concrete elements of the case remain tantalisingly unresolved at the end is this one unimaginative casting decision off the hook.
Black's retirement at the start of the movie, intelligently intercut with the discovery of the body, recalls that of Inspector Prendergast in Falling Down (1993). Like Black, Prendergast is in the last hours of employment with the force, and his successors and superiors treat his insights on this new case impatiently. The Pledge features a cop who has made his pledge to a victim's mother while Falling Down has a detective promising his wife to retire gracefully. Black's decline is more distressing because he has sacrifices the chance of what little happiness he finds, to solve a case. In a further parallel, Falling Down's final scene shows Prendergast's ultimate self-assertion, perhaps reconsidering plans for early retirement. Black's end is one of despair and isolation, talking to himself outside of a dilapidated diner.
It is interesting to consider whether the hero is a victim of fate or circumstance. Is Black's final misery foreordained, or just the result of an unlucky accident? Part of the problem lies in how we take the character of a man who can be his own worst enemy. Like the miniature porcupines offered by the murderer to his young victim, Nicholson's cop is a prickly, independently minded creature. More explicitly, Penn frames the action of the film between scenes of Black's obvious mental confusion, making mental ambiguity a point of narrative reference. Beside the hero, there is the Indian Wadenah (the original suspect in the case), as well as the presumed disturbance of the real killer to contend with. Nicholson's performance is superb, his character alternating between crusty, confused, and convinced.
As his ex-colleagues point out, his retreat into obsessive retirement affects his ability to stay objective. For much of the film he is working 'on a hunch', relying on circumstantial evidence at best. Past experience of such scenarios suggests that such long shots tend to work out correct, but of course we can never be sure. As a disinterested third party, the profiler/doctor whom he visits (Helen Mirren) certainly has her doubts. She questions in turn his chain smoking, sexual dysfunction, and his distinction between reality and fantasy.
Black's abstention from sexual relations, whether forced or not - until he hesitantly embraces Lori (Robin Wright Penn) is in stark contrast to the interview of Wadenah by Detective Krolak. Less of an interrogation than an act of sexual humiliation, Krolak's work is profoundly uncomfortable for Black, on a personal and professional level. One senses that Black is a man who is awkward with intimacy - a further example of his 'disengagement' from normal human relations. The fact that he is willing to sacrifice a possible family of his own just to close the case, says it all. Ultimately, while Krolak reaffirms his status by an aggressive invasion of another's personal space to elicit a confession, Black, broken by what he perceives as private and professional failure, retreats further into himself. The result is a frightening film, dark and adult.