Mira Bai, a 21-year-old Indonesian woman, is found dead near a fish pond at the Pacific Cultural Institute where she was studying. When McGarrett arrives on the scene, he encounters the Governor who is upset, because this institution, which he describes as "an honest attempt to help the emerging nations of the Pacific," was something he fought hard to establish over the objections of a Senate committee when it was proposed.
Mira was strangled to death. There are few other clues. Forensics man Che Fong (played now by Danny Kamekona) finds a footprint which he estimates to be a size 15. He guesses whoever left this print weighed between 210 and 260 pounds.
McGarrett and the Five-O team interview people from the institute, trying to reconstruct Mira's last hours. She had a boyfriend, John Hayes (Denny Miller). After she and John spoke at a dance the night before, Mira suddenly left, "very upset and crying." Mira "had no enemies [and was a] kind, generous, pleasant, hard-working student … in love with John Hayes, who was also in love with her." The 25-year-old Hayes is described as a "superb player" of lacrosse, soccer, football and rugby. He is "6-feet-6, strong as a bull, and wears size 14.5 EEE shoes." McGarrett describes Hayes as "a resurrected Sir Lancelot [who] is nowhere to be found."
Hayes is seen on the beach where he has passed out after a night of heavy drinking. He hears a radio report saying that he is wanted for questioning, so he goes to the Five-O offices and turns himself in. There McGarrett gives him a heavy grilling, especially when Hayes says he can't remember much of what happened the night before. Hayes is totally distraught over Mira's death. He pulls an engagement ring out of his pocket, which he tried to give to Mira, asking her to marry him, but she would not accept, saying she had to go back to Indonesia. Hayes claims this is what caused Mira to be upset.
After he was rejected, Hayes went out and got "stinking, blind drunk." He can't remember what he did, or where he left his motorbike. McGarrett says it is "convenient" that Hayes can't remember anything after about 11:40 p.m., which is around the time Mira died. A bartender named Stanley (Robert Luck) shows up, saying that the "pupule" (crazy) Hayes tore up his place and tried to tear his arm off. The circumstantial evidence, combined with the fact that Hayes is left-handed (Mira was killed by a left-handed person) all adds up, and Hayes is taken away to be booked for murder.
McGarrett returns to the site of Mira's murder near the fish pond at the institute. There he meets a young girl named Miyoshi Kunioshi (Marla Kyo). Miyoshi tells him that two of the koi, "Takahashi-san and Yamamoto-san" are missing: "Both came here from Japan last spring." McGarrett is incredulous she would recognize just two fish from the many in the pond, but she shows him a picture that she drew of them. She says "If you had ten cats and they were all in one room, wouldn't you know if one was missing?" and McGarrett agrees.
When McGarrett returns to the office and asks his men to be on the lookout for these two fish, they laugh at him. He asks for a bucket which turns out to have the same dimensions as an impression beside the pond which was a circle with a diameter of 11 and three-quarter inches. As far as motive for stealing these fish is concerned, Kono tells everyone that "one fish sold for $17,000 last year." McGarrett tells his men to call builders to see if any new fish ponds were installed recently as well as aquarium stores and wholesalers where the fish might be sold.
A homeowner named Fred Babbitt (Jim Demarest) who has only lived in a Honolulu neighborhood for two weeks and recently had a fish pond installed is tracked down. His handyman, Lopez, tipped him off about getting a couple of koi. If you own these, Babbitt says "nobody will be able to tell you from the natives." He paid $237.40 for the pair of fish from the institute's pond. The man who sold him these fish, described as "big as a mountain, [who] didn't look too bright either" was named Benny Apa.
Benny (Ron Feinberg) is located at a cockfight, but he escapes from McGarrett and Kono, running past them like a bulldozer.
McGarrett pursues Benny and attempts to tackle him, but Benny picks up McGarrett and throws him into a ditch, possibly damaging his ribs. Benny runs into a nearby cane field which is owned by Mr. Pindar (Arthur Hee). McGarrett offers to burn off the waste and weeds, which will smoke Benny out, over Pindar's objections. The field is set alight, the place is surrounded by HPD cops and eventually Benny emerges and is taken into custody.
Questioning of Benny, who is "mentally challenged," takes a lot of time, but finally he admits that he stole the fish to make money to buy Chucho, his "champion fighting rooster" who has accompanied him to the Five-O offices. Lopez, the handyman, sold him Chucho for $200 which he got from selling the fish to Babbitt. When Mia surprised him taking the fish and started yelling, he grabbed her by the neck. He goes on: "I didn't mean to have her by the neck. I let her go and she fell down. I ran. I went to work. I thought she was just fainted. She was so scared."
When Five-O asks him how did he get to his job, washing dishes in a restaurant in Pearl City which is miles away from the institute, he tells them "I run some and I walked," first to his house to store the fish and then to his job. When Lopez phones the office, they find out that he gave the keys to his truck to Benny. Further questioning of Benny reveals that he wasn't traveling on foot the evening of the killing, but he used Lopez's truck. The reason that he didn't want to tell Five-O about this was because "I got no driving license."
We then cut to Hayes being released from jail. McGarrett tells Hayes that Benny will be charged with involuntary manslaughter only. Hayes says, "First thing I thought was I'd go to Indonesia, take Mira's place. Take the learning back there for her. What could I do in Indonesia except make myself feel better?" McGarrett asks him, "What could you do in Washington, John?" Hayes replies, "Teach." McGarrett says, "People learn in Indonesia."