Sam Kalakua (John Marley) lives alone in a large old house in the middle of nowhere which has no electricity, surrounded by Hawaiian artifacts. Late at night, he is putting out kerosene lanterns in rooms in the place when he hears a voice from outside calling his name in a ghostly manner. Grabbing a shotgun, he opens the windows to see an apparition. He fires at it three times.
McGarrett is summoned to the Governor's office, where he is asked for a "favor." Sam, who is one of the last descendants of Hawaiian royalty, is in jail because the night before he shot up the neighborhood. The Governor tells McGarrett that because "Sam's regarded by his people as being sacred," he would like Sam released from jail and "to find out what's going on with him quickly and quietly without an official police investigation." The Governor goes on: "You know how proud these old-line islanders are and their feelings about the haoles coming here, changing the face of their islands, and their way of life, all in the name of progress. I'd like to stop any resentment before it starts." The Governor adds that Sam is "a close personal friend." McGarrett tells the Governor that all that he wants will be done.
When McGarrett returns to the office, he finds out that Kono has already bailed Sam out of jail, because he is "a distant uncle," who is "the last of the anointed." When Dano says "Sounds to me like Kono's nine-tenth Hawaiian and one-tenth cop," Kono replies, "My great-grandfather carried a spear for Sam's great-grandfather." McGarrett asks about Sam's behavior with the rifle the night before, and Kono says that he was shooting at Pele, goddess of fire. He drove her off, but she will be back, "a war to the end." McGarrett and Danno are incredulous at this.
McGarrett and Kono go to Sam's place. As they get close on foot, they see Sam's kahuna. McGarrett asks "How can a man cling to the ancient beliefs in this day and age?" Kono tells him, "People got to believe in something, boss. Even if it's a high priest like the kahuna."
Sam is not happy to see McGarrett, saying that what happened the night before "was not a police matter." He says that he was protecting himself from Pele, the goddess of fire. McGarrett begs to differ, wanting to ask Sam some questions. When McGarrett says "I respect your version of it [what Sam related at police headquarters], but I'm a man of this century. I say there is no such thing as the goddess Pele." Sam replies, "My only son was killed in the war. If nothing else, that tragedy makes me a man of this century too. I know what I saw last night. It was Pele. If I hadn't driven her off, I would now be dead."
Sam says even if he goes to jail, Pele will hunt him down there and kill him. He already asked the kahuna why she wants to do this, and the answer was she desires his house to live in, the house of the anointed, the place where the royal ilima (the island flower of Oahu) grows. McGarrett says he wants to help Sam kill Pele off. Sam describes her: "She was ghostlike. Many colors, all shimmering like the fires of hell." There were sounds too: "A wail. A scream. There was discordant music. Once, I heard the rush of lava as it neared the mouth of the volcano." McGarrett confirms he will help Sam, who says "Mahalo."
Kono goes to look at the area where Sam was shooting at Pele, and finds a small piece of synthetic material which is burned around the edges, though there are no signs of a fire in that area. McGarrett pockets this as evidence.
On their way off the property, McGarrett and Kono meet Sam's nephew George (Robert Colbert) and his wife Eleanor (Sally Kellerman). When asked if they can shed any light on what happened with Sam, George says "My uncle's getting very old. I imagine the return to some belief in which he was raised is only to be expected." McGarrett tells him, "I can understand his calling on the big kahuna for comfort but how do you account for a visitation from the goddess Pele?" Eleanor refers to "the Hawaiian dark ages," and says that Sam has had hallucinations before. George says the only help his uncle has had is from his kahuna: "Herbs and those things." Eleanor tells McGarrett that "We've tried, but he won't see a doctor." Eleanor brushes off McGarrett's involvement, saying "Let's consider this a family affair. We'll take care of Uncle." As they leave, George pats McGarrett's arm, saying "The embarrassment of an official mess, we'd like very much to avoid that if we can, okay?"
That evening, the apparition of Pele appears again. Sam is ready with his shotgun. He opens the window, lights a kerosene lamp and throws it outside. It explodes.
The next day, Sam is in court in front of a judge (Robert Brilliande) who has questions about his behavior which could have caused "grave consequences" for both Sam and his neighbors. When Sam protests, "Why should I speak while I am being held here like some caged animal in a zoo," the judge says "This is an informal preliminary hearing to determine whether you should or should not be bound over for psychiatric examination. Remaining silent can in no way help your cause." Eleanor tries to speak on Sam's behalf, but the judge wants to hear an explanation from Sam's own mouth. Sam says that he threw the lantern against Pele in self-defense. Eleanor finally addresses the judge, saying that Sam's beliefs or his sense of mysticism or whatever it is that drove him to his actions, "seems a little more pronounced in him than is normal."
McGarrett, who is also present in the hearing room, makes a proposal: "I ask the court's permission to propose an alternative to an immediate psychiatric examination. A recess of 48 hours. Give Mr. Kalakua's friends and relatives an opportunity to investigate this matter a little more thoroughly. I think that much respect and consideration is due this gentleman who is a descendent of the great kings of Hawaii." When McGarrett says he will guarantee Sam's appearance in two days, the judge adjourns the hearing.
Chin Ho and Kono further investigate near Sam's place, where they find traces of a chemical as well as an oil leak. There are no signs of burning where the kerosene lamp exploded.
Danno goes and talks to Barney Glazer (Peter Leeds), a real estate developer who says that "Kalakua's ten acres is worth a gold mine." He has made multiple offers to Sam, and his brokers were chased off the property by Sam holding a rifle. Glazer tells Danno, "I'd be willing to put out $100,000 in cash as a finder's fee to anyone who can convince that kook to sell that property to me."
Danno further investigates, finding that "there's a note on George Kalakua's business for $150,000 secured by a chattel mortgage" which is held by Glazer. Kono checked out the material he found at Sam's, which is a "special kind of shiny fabric used to make movie projection screens," and Chin says the exploding lamp contained "magnesium, sulfur, nitrate, just a little kerosene ... Chinese New Year's stuff." McGarrett describes all this as "Quite a combination." As they prepare to head out to further investigate, Danno tells McGarrett, "They'll have to kill that old man to get him out of there." McGarrett says, "I I think they tried."
McGarrett goes to see Elanor. He tells her that they think Sam is the victim of a conspiracy: "We think that someone's using his deep beliefs, his primitive commitment to the supernatural, to gain control of his property." As to the implication that she and George are involved in this, she says "If we're guilty, it's stupid. And if we're innocent, it's insulting." She has a theory of her own: "Uncle is growing senile. And his superstitions bring on the visions of Pele and those superstitions may cause harmful injury to himself or to others. If the psychiatric examination bears me out, they'll have to appoint a conservator. And if it doesn't, no one could be happier than George and me. So why don't you go play cops and robbers someplace else? And stop bothering me about that poor superstitious old man."
That evening, Kono, Chin Ho and men from HPD are doing surveillance outside Sam's place while Sam is inside reading. Chin asks Kono if he believes in Pele. Kono replies, "I ain't believed in Pele since I was 4 years old. You know, I suddenly feel like I'm 4 years old." Sam is drinking something, and his vision suddenly gets all blurry. Pele appears again, right in front of Sam inside his house. He falls down in a corner, screaming.
Sam is rushed to the hospital where a doctor (Robert Costa) tells McGarrett "Heart action and respiration indicate deep shock. Tests show some kind of a drug in the bloodstream. Probably hallucinogenic. Condition's critical right now."
Danno has discovered the projection screen material Kono found at Sam's place, called "French lite," is being used by the only movie company shooting on the island. The next day, Danno goes to the location of this company, which is called "Theater of Madness." This outfit is making some artsy production under the direction of Alistair Kemp (Jerry Cox), a doped-out individual who sports a peace sign medallion. Danno hauls Kemp down to the Five-O office under the pretext of "using public property for commercial purposes without a license." Kemp cannot stop laughing. Danno asks him, "What are you on? Pills? Acid? What?" When Danno shows Kemp a sample of the screen, he says, "I get great effects with it." Even when Danno suggests Kemp might be charged with murder if Sam dies, Kemp provides them with no information at all.
McGarrett gets a phone call from the hospital saying Sam has escaped from the place, leaving a note saying he was going somewhere to die.
George and Eleanor meet with Glazer on a golf course. Glazer says they have a big problem because McGarrett had Kemp picked up, despite the fact the director, described by Glazer as an "acid head," told them nothing. Glazer says he wants Sam's 10 acres and he wants it within 24 hours. George suggests Glazer wait until his uncle is declared incompetent, but Eleanor has other ideas, otherwise Glazer will take their business and their house. After Glazer leaves, Eleanor tells George, "There is one thing we can do in 24 hours ... we can kill him."
Chin tells McGarrett that Sam knows the island like nobody else – "caves, ravines, forests that ain't been found yet." Sam goes to a place where he played as a child to pray. Sam tells George, "Pele will no longer be denied. She will have my life after the sky grows dark." He is seeking his kahuna's final blessing, to sustain him in the fires of Pele's world. Sam has searched for him everywhere, but fears that he will not find him in time.
George offers to take his uncle to the kahuna, who he says was seen meditating on The Pali, a place on Oahu where there are very high cliffs. Sam says he can get to The Pali in a manner which will totally avoid the police.
Danno returns to the movie production company's site where he snoops around a room containing reels of film. As Kemp creates some abstract painting with spray paint outside as his followers ooh and aah, Danno examines what is on some of the reels. He is suddenly interrupted by Kemp, who calls the cast and crew to come and help him. Danno pulls out his gun and takes Kemp away on a charge of conspiracy.
Back at the office, the film is screened, revealing scenes of Pele which scared Sam nearly to death. McGarrett reverses and freeze-frames the film which reveals Eleanor as Pele. Kono rushes into the office, saying one of his cousins just spotted Sam on his way up to The Pali. McGarrett and Dano rush out of the office and head there by car.
Sam is seen climbing up to a high place on The Pali, looking over the view and the mountains above which are shrouded with clouds. He calls to the kahuna: "Show yourself to your son, the anointed one! Bless me, great priest, so that I will have the strength to withstand Pele's fiery breath." But the kahuna is not there, only Eleanor in her Pele costume. She calls to Sam: "The kahuna will not come to you. It is I, Pele, who has come for you. I have come for you, Sam Kalakua. You can not defy me! Your doom awaits now."
Sam stumbles towards her and the edge of the cliff, but as McGarrett and Danno suddenly appear, Eleanor is surprised and she falls over the cliff to her death. McGarrett grabs on to Sam, who says "But Pele is not mortal. She cannot die." McGarrett responds: "But your niece is. And she has died."
The show ends with Sam's property being turned into the Honolulu Children's Hospital through the Kalakua Foundation. Sam wonders what will happen to George; McGarrett says that he will stand trial along with Kemp and Glazer. Sam tells McGarrett, "I am not a vengeful man. Forgiveness is a way to heaven." McGarrett tells Sam his father used to say "'Tis easier for the generous to forgive than for offense to ask it." As far as Pele is concerned, McGarrett tells Sam "She won't bother this house again, because it doesn't belong to either of you. It belongs to the future."