When a tourist sees Eadie Hastings (Susan O'Connell), an 18-year-old girl on a rocky ledge high above the ocean, the cops are called, and soon after this, Danno shows up. Danno tries to convince Eadie to come back up, but she is obviously high on something, saying things like "You've gotta love everybody," "Heaven, that's beautiful," and "That's the music of the stars." Eadie doesn't listen to Danno, and jumps off the ledge to her death.
In the Five-O office, McGarrett, Chin and Danno go through Eadie's meager possessions, which include 3 pills that McGarrett says are likely methamphetamine. He says that Danno seems "up pretty tight." Danno regrets he was unable to help Eadie, to which McGarrett reponds, "Let's keep the next one from slipping away."
Chin asks why is Five-O interested in drugs when that is the purvey of Narcotics at HPD, and McGarrett says, "These islands are beginning to bust at the seams with this stuff," detailing some recent horror stories related to speed: "Three high school kids on Molokai beat a harmless derelict to death because they thought he was the devil," and "Another kid on Maui killed a cop because he thought he was looking at him funny."
McGarrett goes to see Eadie's father Ralph (John McLiam) who is furious, telling McGarrett he isn't doing a good job finding out "who's supplying these innocent kids." Hastings goes on: "Whoever it was, whoever did this to Eadie, you find him because he killed her. He killed my little girl, and somebody's got to pay for it." McGarrett also talks to Eadie's mother Sara (Doreen Lang). He says in Eadie's address book found in her handbag, the name of Donna Wales was underlined. Mrs. Hastings says Donna was Eadie's best friend, "a lovely girl [who] wouldn't know anything about taking drugs. No more than Eadie would have…"
McGarrett goes to see Donna (Brenda Scott), who is swimming in the pool at the beachside house of her parents. She calls McGarrett "fuzz" and when he asks her why Eadie jumped off the cliff, Donna tells him, "I think she jumped to get out of it. But you're such a rock in this rotten establishment, you couldn't understand that, could you?" Looking at her parents' place, McGarrett tells her, "Yeah, this rotten establishment's really kicked you around." Donna says, "This is where my family lives. It's their scene, not mine." McGarrett says, "I'm here for information, information that might help a lot of other kids like Eadie." Donna replies, "Oh, and how would you help them? Would you use the end of a nightstick or the end of a gun barrel?" He tells her, "You've been reading too many leaflets," and continues, as he is leaving: "You know, it's funny. Your best friend is dead and you can help us find out why and how, but you couldn't care less. That's pretty cool, baby, pretty cool."
Rattled by what McGarrett said, Donna goes on her motorbike to see David Stone (Ed Flanders), who is supplying people like her and Eadie with drugs. She tells him, "I'm frightened, I need you." Chin Ho follows Donna. At a conference later in the Five-O office, Danno reports that Stone was formerly a professor who was "kicked out of a mainland university for turning half the student body on. He was handing out experimental drugs like they were bubble gum. He was allowed to resign from his post for conduct unbecoming a teacher."
McGarrett goes to see Stone, who rationalizes what has happened in a very slippery way. According to Stone, Eadie was a "wonderful girl" who "was searching for who she was, for light, joy, the vision of truth, the central experience." She was "dropping out … of the rat race, sordid little games you people play and call life." When he accuses Stone of killing Eadie, Stone tells him, "The stinking, rotten society, your establishment, killed her." McGarrett says that Eadie "was shot full of speed, her brain so scrambled she thought she could walk on a cloud," but Stone says, "That's not my responsibility. I told her. I tell all my children, never take a trip without a guide." When McGarrett suggests that Eadie took "a few too many speed pills," Stone pleads ignorance, and tells McGarrett not to try and entrap him: "I have no idea how, where or from whom Eadie got the dosage of speed, acid or whatever it was that freaked her out." When he accuses Stone of, in effect, pushing Eadie off the cliff, Stone says, "I'm truly sorry for what happened. But there can be detours, roadblocks, unfortunate accidents, even when one is taking the right direction." Stone tells McGarrett to get lost, and "next time, bring a warrant." McGarrett replies, "I'll do better than that, professor. I'll bring a pair of handcuffs."
Back at the office, McGarrett talks to Chin and Danno how Stone is a "prime suspect" who could be busted on four possible counts: "Possession of drugs, manufacture, use on premises, and apprehended in the act of passing," but there is no way they could make any of these charges stick.
McGarrett realizes they need "somebody on the inside" but before they can do anything about this, Eadie's father bursts into the office, freaking out, wondering why they haven't found the man who killed his daughter yet. McGarrett assures him, "If there is a man, we'll find him and we'll put him behind bars. But it'll be done legally." After Hastings leaves, McGarrett tells Danno, "You're gonna take up the simple life."
Danno becomes a beach bum and befriends Donna, who runs into him. He tells her the "fuzz" don't like him doing his thing, like living in a beat-up truck and cooking his meals on the beach. When Donna asks him what is his "thing," Danno replies, "This. If I get tired of this beach or somebody runs me off, there's always another one." When Danno asks her what is her "bit," she responds, "The sacred weed, marvelous mushroom." Donna takes Danno back to her parents' place, where one of her pals, Zero (Gray Gleason), tells her that there is a "ball" at "the prof's pad" that evening. Donna and Danno go to Stone's house later, but he is not there. Donna is distraught, saying, "David, I need you." Though she tells Danno to leave her alone, he takes her home.
When Donna returns to her place she finds Stone there. He slaps her in the face, because Zero recognized Danno as one of the cops who checked up on Eadie's friends including himself after her suicide and Donna brought the "fuzz" to Stone's place. Feeding Donna some drugs, he tells her, "You're going to learn the difference between the insight I've given you and just turning on for kicks. And the way to learn that is to experience your trip all alone." Donna says that she cannot take a trip alone, but Stone leaves her. She is next seen riding her motorbike while hallucinating. She winds up on a beach, where she is later found and taken to the psychiatric ward of a local hospital where there are several other women patients. When she screams and tries to escape, orderlies grab her and strap her to her bed.
Donna awakens with McGarrett, Danno and a Doctor Fuller (James C. Bertino) at her bedside. She is not happy to see Danno, who tells her, "Speed usually ends you up something like this, and it's my job to try to stop this from happening." McGarrett tells her, "You were really turned on, young lady. It's a wonder you didn't kill yourself."
When Donna wants to know where she is, Fuller explains, "You're in a hospital ward for acidheads, speed trippers." Donna says she will only take "guided tours" in the future, but Fuller shows her one woman who was on a guided trip and has been in the hospital for six months and "we can't get through to her." McGarrett shows Donna another patient, Rachel, who Donna knows. Rachel is completely unresponsive. McGarrett tells Donna, "If someone like you had helped us months ago, Eadie and a lot of other Eadies might have been saved. This girl would really be going to school instead of living like a vegetable in a mental hospital."
Later, at home, Donna gets a call from Stone. She tells him that she had a "very bad trip", she has "learned her lesson," and she wants to see him that evening. Then she phones McGarrett.
However, this plan is disrupted by Eadie's father, who confronts Stone at his place with a loaded gun. Eadie's mother found a diary while going through her daughter's things which he father says was "full of the filth you taught her." He forces Stone to read a passage: "Time stops while I learn the meaning of love and we become one. I and thou... To my beloved guru, David Stone, in whose arms…"
Stone tries to reason with the father, who says that he wants "some of that stuff you gave to Eadie." Stone gets some pills, and he offers one to Hastings, saying "Put away the gun … find love, peace," but Hastings forces Stone to eat not just that pill, but three more. Stone knocks Hastings down, and escapes, taking the gun.
The doped-up Stone takes a trip of his own, including a hallucinogenic light show. He almost gets run over by a couple of cars, wanders through a run-down part of town and winds up in a cemetery, then makes his way to Donna's house, pleading for help. He thinks Donna is laughing at him, which she is not, and that Donna has become Eadie. He asks her, "Did you find what you were looking for?" Stone leaves, dragging Donna with him to the place where Eadie committed suicide.
McGarrett and Danno arrive there soon, alerted by a cop. As McGarrett talks to Stone, the professor gets philosophical: "The two greatest adventures of mortal man [are] being born and dying. And having experienced the first, I long now for the second, and, I believe, greater of the two adventures ... death." Despite the fact that Stone still has the gun, McGarrett manages to grab his arm and, with the help of Danno, Stone is taken into custody.