Dan Larsen (Don Knight) is being pursued at high speeds by a police car out in the countryside. With him is Celeste Caro (Josie Over), who seemingly regains consciousness and starts to attack him. She eventually jumps out of the car to escape him and rolls to the side of the road as Larsen speeds away.
Later, McGarrett arrives on the scene along with the Consul-General (Ed Fernandez). When an HPD cop gives McGarrett an expensive-looking earring that Celeste was wearing, McGarrett asks the Consul whether this was "part of the stuff you might be looking for." The Consul says, "Yes, it is ours." McGarrett asks an attending doctor what are Celeste's chances. The doctor shakes his head negatively. Before she expires, in response to McGarrett's questions about where she got the jewelry, Celeste whispers several times, "The ways of love..."
The Consul-General tells McGarrett that he never saw Celeste before. He is concerned that the crown jewels from his country -- which were displayed in Hawaii only after considerable hesitation -- have not been recovered, having been stolen 8 days before.
Celeste's landlady tells Williams about Larsen kidnapping Celeste. She called the police as Larsen -- a "blond man" -- dragged Celeste to his car. McGarrett arrives and the Five-O crew check out Celeste's room, which contains several of her paintings and sketches. A piece of paper in an envelope addressed to Dave Barca, Box 2469, Solareo, California, reads "Dear Dave, The ways of love are strange. The vows of love." An envelope containing unexposed X-ray film is found.
Back at the Five-O office, the Attorney-General Walter Stewart (Morgan White) pushes McGarrett to recover the missing jewels because he is getting "pressure from Washington." Danno has determined that Dave Barca's address is a county jail where Barca is waiting for a hearing on fugutive charges. Barca was picked up in Honolulu two days after the jewel theft, charged with parole violation. He was caught going through a red light, driving Celeste's car without a license. Barca served time in San Quentin for felonious assault and forgery. Stewart asks McGarrett if he wants to go to the mainland.
The next scene takes place in Barca's (James Patterson) cell in California. McGarrett enters in disguise as a prisoner named "Steve Crowley."
McGarrett as Crowley says he just got out of a "lousy Air Force jail." He has been arrested for armed robbery.
In Hawaii, Larsen's car is dredged out of a river. In the trunk Five-O finds X-ray equipment.
The chatty "Crowley" is getting no response from Barca, trying several ways to befriend him.
In the Five-O office, an X-ray technician named Jimmy (Robert Costa) says the equipment recovered from the car trunk looks like the kind which can see through heavy steel plate.
McGarrett listens to a radio in the cell. A news item (bogusly inserted) tells about the Honolulu jewel robbery and how Celeste was killed. McGarrett has an appointment with the prison dentist.
McGarrett plans his strategy with the help of prison officials. He takes a knife from the "dentist's" office. Back in the cell, McGarrett shows Barca the knife, and says that during his court appearance the next day, he intends to "leave."
In the Five-O office, Jimmy demonstrates how the X-ray machine can see through a safe to determine the combination. Using the resulting picture of the tumbler action, Danno opens a test safe.
While on their way to court, McGarrett and Barca overpower a guard in the elevator and escape over the prison roof. As they flee, guards fire shots at them.
At his "girl friend's" place, McGarrett looks for money. He mentions the free flights which Air Force people can take. Barca wants to know more.
In Hawaii, the body of "Jack Wade," an X-ray technician known for preparing fake X-ray plates to falsify insurance claims, is found dead on the beach. One of his partners is known to be Larsen.
Barca wants to go to Hawaii using the Air Force flight scam. McGarrett says they have to catch a plane at nearby Travis Field. Barca convinces McGarrett to go by saying "I'll make you rich." McGarrett tells Barca they need mimeographed flight orders. They break into a printing company and manufacture these papers.
The two men arrive in Hawaii, followed by Danno and Kono, and take a cab to a boat called Scuba Belle anchored at a marina. Barca looks unsuccessfully for the jewelry under the floorboards. He tells McGarrett that he'll pay $25,000 to help find Larsen. He gives McGarrett a gun.
McGarrett, driven to Larsen's place by Danno and Chin, knocks on Larsen's door, pretending to be drunk. When Larsen opens the door, he forces Larsen at gunpoint to come back to the Scuba Belle, where Barca beats Larsen, trying to get him to reveal the location of the jewels. Larsen says Celeste never told him anything.
Using Larsen's girl friend's car, the three men go to Celeste's place as the Five-O team -- who are following them -- hide outside. Barca finds the "ways of love" message, and shoots Larsen, saying that Celeste never double-crossed him. Five-O lays low while Barca and McGarrett escape.
Barca and McGarrett go to a temple near the ocean. Barca tells McGarrett to wait in the car, but McGarrett follows him and watches as Barca talks to a priest. The priest says that "the girl" that Barca came with before left him something. He gives Barca a box which contains the jewels. Barca looks at the jewels by the ocean. When McGarrett speaks up, Barca draws a gun, and McGarrett shoots him. McGarrett identifies himself as a cop as Barca expires, saying, "The vows of love ... she did love me."