As the show begins, we see a man walking through a cemetery carrying a guitar case. The camera focuses on his hands, which are metal hooks. As he continues walking, the scene cross-cuts to a funeral procession led by the policeman Keoki. Hookman continues across the cemetery, climbs over a fence and up on top of a hill. The funeral procession works its way out of town, up a hill and then down through a tunnel. Hookman assembles a rifle and takes aim at the tunnel entrance. After the funeral procession emerges from the tunnel, he shoots Keoki. The hearse runs amok, ramming another car. The casket falls out on the street and the widow screams.
The Five-O team and members of HPD arrive at the top of the hill where Hookman was shooting. Chin Ho examines the weapon, which is an M-1 rifle of World War II vintage with Keoki's name on an engraved plate attached to it. When McGarrett arrives, he is unusually agitated, saying "This guy is sick."
Back in the Five-O office, McGarrett talks to Keoki's friend Ookala, wondering whether Keoki was on the take. Ookala says that Keoki "didn't owe anyone a dime," which is "why he had the Saturday funeral job." Ookala says he will work around the clock to find Keoki's killer, and McGarrett says so will he.
Later, Chin Ho reports that Che Fong is trying to trace the rifle from Army and FBI records.
In his fleabag hotel room, Hookman eats a TV dinner while listening to a police radio scanner. The camera shows three more M-1 rifles on his wall. The newspaper arrives, and Hookman cuts the large banner headline -- "Officer Killed by Rooftop [sic] Sniper" -- and pins it to his wall.
Che Fong has determined that the lettering on the metal plate doesn't line up, and that the "O" is made with a chipped tool. He says it is hand stamped with a steel lettering set, not engraved. McGarrett tells Danno to make up a bulleitn to try and find out who sells gold plates in Honolulu. The rifle was traced back to 1943 when it was used by Patton's Third Army in France. Thousands of GI's smuggled them home. Che says the serial number is still visible on the rifle used to kill Keoki.
Back at Hookman's room, we see him stamping another metal plate with Ookala's name on it.
The scene switches to a wild shootout which brings numerous members of HPD and all the Five-O team except McGarrett, who is with the Governor. The crazed gunman calls the police "pigs" and calls Danno "big mouth" when the latter uses a bullhorn to try and persuade the gunman to surrender. Duke wonders if this gunman is the killer of Keoki, but Danno doubts it. Tear gas is used to flush out the gunman, who fires at the police and dies in a hail of bullets. The gunman's rifle is an M-1. Suddenly it's revealed that Ookala, who is at the scene, has been shot and killed. Danno radios the governor's office, then McGarrett's car, suggesting that maybe the gunman was the sniper after all. McGarrett is disturbed when told of Ookala's death.
After doing an autopsy on Ookala's body, Doc reveals that Ookala died from intestinal hemorrhaging, and the bullet passed down through his chest. Chin Ho discovers that the gunman was a smack pedlar and says that the "drugs scrambled his brain." McGarrett and Danno return to the scene of the gun battle and discover another rifle on the roof of a building nearby with Ookala's name on a metal plate.
On the rooftop, as HPD dusts the rifle for fingerprints, McGarrett says of the killer "He's a maniac ... a psycho." They determine that the killer knew Ookala's movements with the help of a scanner. McGarrett says he wants "the book" on both Keoki and Ookala.
Later at the office, the Five-O men report they have been checking records of the rifles, but have no leads. They also report that Keoki and Ookala were involved in over a thousand incidents
Again we see Hookman stamping letters on a metal plate, cross-cut with a scene of McGarrett talking to the Governor. The Governor wants to "take the heat off" McGarrett.
Che Fong determines that the "O" on Ookala's metal plate was produced by the same tool as that used to make Keoki's. McGarrett wants to redouble efforts to locate the source of the plates. Danno says that they may have located such a place at Norm's Jewellers.
Hookman is seen walking down a hallway in a building, and he opens the door to a room. In the next scene, McGarrett and Danno meet with Norm the jeweller, who determines that he made the gold plates four or five years before. Unfortunately, his records don't tell who purchased them. Back in the apartment room, Hookman is seen taking aim at Norm's store which is below. He is interrupted by a maintenance man who enters the room and sees the rifle, but using his hooks, he deals the man a blow on the head. Hookman returns quickly to the window. As McGarrett and Danno leave the shop, Norm says that he never called Five-O just as Hookman showers bullets at the front door.
McGarrett and Danno retreat into the jewellery store. After a few moments, the shooting stops, and Hookman retreats down to ground level, where he gets into his green Mustang and exits from the building, almost running down McGarrett in the alley. McGarrett jumps into his car and gives chase at speeds approaching 100 miles an hour. Hookman makes his way to the dock area where he drives up onto a loading ramp and then narrowly gets past a dump truck which cuts McGarrett off.
Hookman returns to his room with cuts on his face and missing one arm.
At Doc's office, McGarrett engages in the usual banter about "simple English" as Doc explains further about Ookala's wound.
Hookman's Mustang is winched out of the harbor. When McGarrett arrives, he finds an arm with a hook hand grasping the steering wheel. Suddenly McGarrett figures out what is going on. He realizes that Larry Thompson, Ookala's partner is next on the sniper's list. He radios central dispatch to contact Thompson, but they say that Thompson is off duty. When Danno arrives a few moments later, he says that Thompson is dead, killed in a similar manner to the other two men. McGarrett says that the killer is Curt Stoner.
At the Governor's office, McGarrett discusses the case. About 12 years before, Stoner was involved in a robbery of the Oahu National Bank. McGarrett and the three policemen were the first on the scene, and during the ensuing gunfight, Stoner's hands were blown off by explosives which he was holding to extort money out of the bank. Stoner got a sentence of "10 years to life," but was paroled. McGarrett figure that Stoner will lay low, and that Five-O is going to "check the low rent districts." He figures that a man with hooks for hands "can't hide them very well."
Stoner is seen preparing another rifle for McGarrett as the Five-O team talk to people living in his neighborhood. He sees McGarrett and Danno out the window. McGarrett and Danno check out a hallway where a mailbox has a nameplate with S. Brock on it. Using his magnifying glass, McGarrett determines it's made with the same lettering tool as the other plates. He sends Danno for help as he goes up to Stoner's room, where he kicks in the door. On the wall he sees the headlines cut from the newspapers, some German medals in a display case and various newspaper articles about Stoner.
The phone rings and McGarrett picks it up. Stoner says, "Hello, McGarrett, I've got a present for you ... look in the bureau drawers." (These are the first words heard from Stoner in the show.) McGarrett opens the dresser carefully, to see a set of hooked hands with his name on metal plates attached to them. He ducks as a rifle shot hits the door. Picking up the phone again, he hears diabolical laughter from Stoner.
McGarrett looks across the street where Stoner emerges from the building and climbs the fire escape to the roof. Danno shows up and the two of them go down to street level, where other cops, including Ben and Duke arrive. McGarrett gets Ben to draw Stoner's fire while grabbing a rifle from his car trunk which he tosses to Danno. He then drives away, causing Stoner to stand up and shoot. Danno kills Stoner, who throws his rifle to the ground. McGarrett returns and picks up the rifle. Both he and Danno seem momentarily stunned by the events of the past few minutes.