After singer Bobby George (Sal Mineo) ends a set at the Swinger nightclub, two women (Carol Ann Leslie and Janice Teramae) follow him backstage to get his autograph. Two armed men masked with nylon stockings over their heads -- Jerry Parks (Sam Melville) and Allen Brent (Ion Berger) -- grab Bobby and hustle him out of the place past a dishwasher (Francis Dawson), who is punched out, and a chef (Moki Palacio) who comes after them with a butcher knife. They drive away in Bobby's car.
Five-O and HPD under Lieutenant Jasper (Clif Eblen) soon arrive at the club. McGarrett grills Ted Harmon (Robert Luck), its manager, who says that Bobby "didn't draw the crowds ... he was a flop." McGarrett wonders if Bobby owed money to anyone or was a gambler or drug user, all of which Harmon denies.
McGarrett and Danno go to Bobby's apartment where they meet Carol (Heidi Vaughn), Bobby's girl friend. She is incredulous that anyone would want to kidnap him. Danno finds an envelope from D.J. Georgiade (Harold J. Stone), a well-known hotel magnate. Carol says that Bobby told her he changed his name from Georgiade to George and that D.J. was his father, which she did not believe at the time.
Bobby's kidnapping is breaking news on KGMB which makes the connection between Bobby and his father, "the owner of the big Georgiade hotel chain," who is on his way to the islands. At their hideout, the two kidnappers are watching this broadcast with Bobby. Parks describes Bobby as a "star," adding "There won't be a club or a TV show anywhere that won't be begging you to sign."
The three men all laugh, and we realize that the kidnapping has been nothing other than a publicity stunt.
Bobby's father arrives the next day at the Honolulu airport on a United Airlines flight. Despite McGarrett cautioning him not to say anything to the press, Georgiade tells reporters that he means to "rectify this situation" with the help of Peter Taylor (Richard Gossett), head of his company's security forces. He offers a $5,000 reward for information relating to the kidnapping with "no questions asked" and a "complete guarantee of secrecy."
At the office of the Hawaiian Attorney General (Morgan White), Giorgiade lambastes local efforts to find his son, saying that they consist of "red tape, silence, [and] platitudes." McGarrett tells him "The greatest enemy your son has right now is you," adding "we will find him, unless you blow it by offering to exchange a bag full of money for a bullet in his head." As McGarrett is called away, the Attorney General tells Georgiade "In McGarrett, you've got the best. Believe me, the best."
At the Five-O offices, the team listens to a reel-to-reel tape which Carol found in her mailbox. On this tape, Bobby tells her to get his father to come to Hawaii. There is a mention of "money." Bobby is worried that he will be killed. McGarrett tells Danno to take the tape to TV station KGMB and get Charlie Grey (Dave Donnelly) to analyze it.
Back at the kidnappers' hideout, Parks sadistically threatens Bobby with a knife as a joke.
McGarrett and Danno go to KGMB. Danno has already identified the local store where the tape was purchased as Beatty's. On an oscilloscope-like device, Charlie shows them that there is a "high frequency signal coming from the microphone, the mike cable, or some kind of interference from the set itself." Danno takes a call from Beatty's, who says that Bobby bought a lot of that particular brand of tape.
Bobby's father goes on KGMB, addressing the kidnappers: "I mean to cooperate with you as fully as I can ... I will pay you anything you ask. Anything for the release of my son."
At their hideout, Parks asks Bobby "How much do you figure you're worth to your old man?" Bobby says he just wants to get the hoax over with and to leave. But Parks has other ideas; he wants to go through with the kidnapping for real and get ransom money. When Bobby realizes what is going through Parks' mind, he attempts to escape, but is pursued and captured.
At KGMB, Charlie demonstrates to McGarrett and Danno that the tape Carol received from Bobby was recorded on the same machine as one of the other tapes recovered from Bobby's apartment.
When McGarrett tells Georgiade that the kidnapping was just a publicity stunt, the father admits he is estranged from his son, but he takes care of him financially. McGarrett says "You don't know him any better than I do and I don't know him at all." Georgiade offers to pay for all the police work which has been done so far, but McGarrett tells him, "No chance."
Meanwhile, the case is getting nowhere as far as leads are concerned. A second tape is received by Georgiade, who brings it to the Five-O offices. On this tape, Bobby says, "Dad, they're gonna kill me if you don't give them half a million. They heard you on TV, ou said you'd pay anything." He tells his father the money has to be produced within 24 hours.
McGarrett goes to meet a couple of "swingers" on the beach (Karol Kai and Susan Kay Logan). They are close friends with not only Bobby, but also Parks and Brent, who they recently drove to the airport to fly to Los Angeles. At their hideout, Parks and Brent talk about flying back to L.A. using the same phony names they used to return to the islands prior to the kidnapping. When Brent asks Parks if Bobby will spill the beans to the cops after they leave, Parks says not if they kill him. Brent is not happy about this scenario.
Further analysis of the tape at KGMB reveals a Hawaiian song in the background as well as the sound of an airplane. Using these two clues and checking with local radio stations and local airports, as well as using the transparent board with a map in McGarrett's office enables the team to narrow down the area where Bobby is likely being held to the Wahiawa District, but it is still a very large area.
There is no idea as to how Parks and Brent could have returned to Hawaii from the mainland, though McGarrett is suspicious that they left town just to set up an alibi. McGarrett is clever, though, surmising that whoever mailed the tapes was using the bus, since the two men's cars are sitting unmoved in their garages. McGarrett gets Bobby's father to make another plea on TV to the kidnappers, saying that the part of the second tape with instructions about where to deliver the money was damaged. Of course, Parks and Brent see this news flash.
With seemingly unlimited police resources, some of Jasper's men ride buses, where they encounter Brent taking the Waipahu bus on his way to mail another tape. McGarrett quickly shows up and convinces Brent to reveal the location of the hideout, where Parks has second thoughts about shooting Bobby and instead tries to make him overdose on a bunch of pills. At the last moment, McGarrett and Danno show up and Parks is shot.
Now that he is rescued, Bobby tells McGarrett he is sorry. McGarrett responds, "You hotshots are always sorry when the damage is done." He pushes Bobby in the direction of his father, who is standing nearby, and the two men reconcile.