Two punks, Rolly (Paul Koslo) and Tanami (Richard Dimitri) are driving around with Rollie's girlfriend Perky (Nicole Ericson). They stop at a bakery where Rolly gives Tanami a gun. Tanami enters and attempts to rob the owner, Sunada (Harry Chang), who draws a knife and stabs him. Tanami shoots Sunada and stumbles out into the parking lot. Rolly takes the gun and drives away with Perky.
As they drive along the beach, a cop pulls the two of them over because of Perky's erratic driving. Prior to this, Rolly throws the gun onto the beach. Rolly talks to the cop, who decides to let Perky off with a warning.
Back at the bakery, Sunada is loaded into an ambulance complaining that he has been robbed six times.
The crime lab compares the bullet from the robbery to one used to shoot U.S. Senator Kurusu six months before. They are both from an HK 9mm German automatic, a relatively rare gun, which was stolen from another senator and Kurusu's next door neighbor, Roger Bancroft (Andrew Duggan). McGarrett assigns Carew to check on Bancroft, complaining that there are "guns everywhere."
At Bancroft's place, there are numerous friends of his son Elliott (Jack Stauffer) hanging around as the two men practice skeet shooting. There is tension between the two men. Carew looks around the large estate, checking out Bancroft's gun cabinet. He points out that people who have guns have an obligation to take care of them. There are some steep cliffs behind the house leading down to the ocean. Bancroft doubts that anyone could climb up them to steal his artillery. When Carew sees Kurusu's house next door, Bancroft tells him the two men were "violent political enemies" because of Kurusu's attempts to introduce gun control legislation. During this conversation, Elliott keeps interrupting his father, much to his annoyance.
At the hospital, Lori interviews Sunada, who complaints bitterly about having to pay for his stay in the hospital, as well as a lawyer, while Tamaki, who is down the hall, gets everything "from the public trough." Tamaki ridicules Duke, saying there is no gun and therefore no case against him. In fact, he threatens to sue Sunada for assaulting him!
Rolly returns to the beach to find the gun. A brother and sister are playing, and the boy finds the gun. When his sister hides in a box, he shoots her, despite Rolly's attempt to stop him. The children's mother comes over and holds her daughter's limp body.
At the hospital, McGarrett discusses the case with the crime lab technician. He suspects this gun that shot the girl is the same as used in the two previous incidents. McGarrett consoles the girl's mother, who is relieved when a doctor tells her that her daughter will recover.
McGarrett returns to the beach with the boy to find the gun, but they are unsuccessful.
Tanami is released from jail for lack of evidence. Duke tails him to Rolly's home, where Rolly shows Tanami the gun that he recovered at the beach after the shooting. Tanami says that Five-O told him this gun was used to kill Kurusu, and that because of this, he figures they can get a lot of money for it. Rolly and Tanami are fooling around when the gun goes off, killing Tanami. Duke breaks into the house, but Rolly flees out the back door.
Duke finds a 9mm shell on the floor of Rolly's place.
Rolly goes to Bancroft's home, and confirms he lives there by looking in the mailbox. Some HPD cops see Rolly's car and investigate. As Rolly is climbing up the rockets behind the house, one of the cops orders him down, and when Rolly runs in the other direction, shoots at him. The cops attempt to follow Rolly, who escapes through the neighborhood, but they don't find him.
Rolly arrives at Perky's house, where he listens to a police scanner. He's nervous about people passing by outside. He phones Bancroft, threatening that he knows who shot Kurusu, and asks for $50,000 in cash. Rollie then dyes his hair brown with some kind of spray. Perky returns home, but when she opens the front door, the paranoid Rolly shoots her by mistake. As he holds her body, her neighbors attempt to break in. Rolly gets away in Perky's blue Volkswagen.
At an isolated location near the beach, Elliott, who listened to Rolly's conversation with his father on another line, waits with the money.
A helicopter follows Rolly in the Volkswagen and alerts McGarrett and Crew as to his location. Rolly, wearing a Hallowe'en mask, meets Elliott and takes the money. He throws the gun to Elliott, telling him to get rid of it. McGarrett and Carew appear in the distance, and Rolly leaves in a hurry. They force him off the road onto a sandy beach, following which McGarrett grills him.
At Bancroft's house, Elliott, reacting to his father's smothering influence, complains that he has a life of his own and says that he has something to tell his father. However, before he can do this, McGarrett and Carew arrive, saying they now know where the stolen gun is. They accuse Elliot of shooting Kurusu. Elliott confirms this, saying that he did it because he wanted to please his father who said he was going to kill his neighbour.
Elliott escapes to a guest house nearby, where he tries to find ammunition to load the gun and kill himself. Carew breaks in the door and disarms Elliott. Bancroft grabs the pistol and threatens McGarrett, who launches into a lengthy tirade against guns. Finally, Bancroft surrenders the weapon to McGarrett.