***DEFINITE SPOILERS***This is a movie concerning a retiring detective Jerry Black (Jack Nicholson) who, at his retirement party, is involved in the investigation of a brutal rape and murder of a young child that has only just been discovered. When the duty falls to him because the local police apparently refuse it, he tells the parents of the child's death. The distraught mother exacts a pledge that he will find the murderer "upon his soul's salvation". Meanwhile, the police arrest a retarded Native American trapper who had been seen at the scene of the crime and who has a previous rape history. The overzealous officer in charge uses unorthodox tactics to extract a confused confession. The Native American, confused and feeling horribly guilty, kills himself.
Case Closed, right? Not for Black. Black determinedly investigates the murder and interviews the victim's best friend who tells him that the victim had a friend, a "Giant" called the "Wizard", who was giving her little porcupines. The victim had drawn a picture of herself with the Giant and his vehicle which Black steals to use to broaden his growing dossier. Black's investigation uncovers two other cases involving victims with strikingly similar descriptions which have remained unsolved. One of the similar murders happened while the Native American suspect was in jail. He fails to convince his fellow officers that they should keep the case open and although retired, must keep his promise and find out who murdered the victim in this case. He buys a store-gas station in the region in which the murders occurred.
He makes the acquaintance of a local waitress-bartender Lori (Robin Wright Penn) who just so happens to have a young daughter fitting the profile of all the victims. Lori is also a victim, of domestic abuse, and leaves her husband one rainy night after having been badly beaten and seeks assistance from Black. Black invites her and her daughter to stay with him temporarily, "no strings attached" but they eventually move in with him and the story kicks into high gear. The rest of the movie is cut with glimpses of scenes of possible perpetrators and potential clues. Finally, the little girl offhandedly mentions to Black that she met a man called "The Wizard" who has invited her to meet him at the picnic grounds the following day. The little girl shows Black small chocolate porcupines "The Wizard" had given her. Black sets up a stakeout at the picnic grounds with his ex fellow officers. After waiting what they feel is too long, the officers finally tire of the stakeout and leave, but Black is told they intend to tell Lori what is going on.
Lori races to the picnic ground, hysterically confronts Black with accusations and questions he doesn't appear to understand, then takes her daughter and leaves. On the way back to the station, the police officers see a burning wreck with a dead driver. Hanging from the rear view mirror is a tiny porcupine. The movie closes with Black drinking from a pint bottle in front of his closed and quite possibly abandoned store, muttering to himself.