Red Chinese agent Wo Fat uses a sensory deprivation chamber to procure information from U.S. agents. McGarrett, head of Hawaii's state police force, poses as "control," possessor of the names of other agents. He allows himself to be captured and placed in the chamber; will he be able to withstand the torture?

Five-O investigates multiple cases of missing women tourists. The victims were all recently widowed. It turns out that they are being seduced, swindled and then murdered. Five-O sets up an undercover operation in which a Honolulu Police Department woman officer will serve as bait. The culprits are a married couple. He seduces the victims, she pretends to be his sister.

A state official is killed by a bomb after arriving from a visit to the Mainland. Five-O discovers the official had more enemies than it initially appears.

A young singer is kidnapped shortly after a performance. The singer's father is a hotel magnate from the Mainland. However, the crime began as a hoax, and the two kidnappers are friends of the singer. Once the hotel magnate offers a big reward, the friends decide to collect -- at any cost.

The primary witness before a grand jury investigating a Hawaiian crime figure dies suddenly on the stand. At the same time, assassins from Japan are trying to kill the accused criminal. Five-O has to figure out the accused man's secret and why killers from Japan are after him.

Danny Williams is indicted and jailed after an off-duty pursuit leads to a suspect's death.

Five-O investigates a gold-smuggling ring. One young woman is already dead as a result of the gold smuggling. Five-O and the U.S. Treasury Department devise a sting operation aimed at nabbing Johnny Fargo, a brash operator, and the wealthy attorney who is the brains behind the operation.

During a high speed chase, a woman jumps from the car which the police had been chasing. McGarrett arrives to hear her dying words, "The ways of love." She was also somehow wearing a diamond earring that was part of a display of a foreign nation's Crown Jewels which were stolen while in Hawaii a few days earlier. At the dead woman's home, there is a letter addressed to Dave Barca, who is incarcerated in a California jail but who had been in Hawaii when the jewelry robbery occurred. McGarrett goes undercover, posing as another prisoner at the jail in California. Meanwhile, Danny Williams and other 5-0 officers find specialized X-ray equipment in the now-abandoned car involved in the chase. It turns out the thieves used the X-ray equipment to discover the combination of the safe that housed the jewels. Now, it's up to McGarrett to use Barca to find the jewels.

McGarrett is investigating a cat burglar who pulls off jobs in spectacular fashion. His most recent heist totaled $30,000 of jewels from a room in a high-rise hotel. The culprit is Joey Rand, a lounge singer who's also a compulsive gambler who owes a Mainland syndicate $200,000. His girlfriend, who works for a company that does tours, supplies Joey with the names and room numbers of well-to-do people. Joey is now the target of a determined McGarrett and the syndicate that's ready to kill him over the singer's gambling debts.

A U.S. serviceman, in Hawaii for R&R, becomes a pawn in a fight for control of a numbers syndicate. The head of the outfit, Philip Lo, is killed and the serviceman has been framed for it. McGarrett & Co. race to solve the killing, shut down the numbers syndicate and prevent the serviceman from becoming the next homicide victim.

McGarrett is gunned down during his morning run on the beach. While the lawman is in critical condition, Dan Williams leads the investigation. Shortly thereafter, another man is killed and Five-O probes whether the two incidents are related. It turns out they are -- and the state Attorney General may become the next victim.

An assistant district attorney is killed when he finds a ''box man'' i.e. safecracker rifling through the attorney's office on a Sunday. The assistant DA was preparing to prosecute Matsukino, a local mobster. The key piece of evidence, a handgun, is now missing. McGarrett brings in Matsukino and his right-hand man, Cardonus. McGarrett does a bit of psychological game playing by letting Matsukino go and keeping Cardonus in the lawman's office. The Five-O leader reminds Cardonus that Matsukino doesn't like to leave loose ends. After Cardonus is released, his car blows up. Cardonus, knowing that Matsukino wants him dead, goes to Five-O. McGarrett wants Cardonus to testify at the upcoming trial. The question is whether Five-O can keep Cardonus alive to make the court date.

A young woman student from Indonesia is killed at an educational institute. Footprints at the crime scene indicate a large man was present. Five-O comes up with two suspects: her American boyfriend and a mentally challenged man, Benny Apa. Neither case is airtight. The boyfriend had an argument with the dead woman shortly before she died. Benny Apa confesses to the killing but McGarrett can't be sure if he knows what he is saying.

A returning soldier that saw combat in Vietnam returns to Hawaii and has a severe flashback that leads to him taking over a hospital including Dan-O as a hostage.

Dan Williams is unable to prevent a young woman high on drugs (referred to as speed but which have the properties of LSD) from jumping off a cliff to her death. The incident puts Five-O on the trail of Professor David Stone, who was kicked out of "a Mainland university" for enticing students into using drugs. As McGarrett is building his case, the dead woman's father confronts Stone and forces him to take a large dosage of the drug. Stone ends up on the same cliff and now McGarrett attempts to save his life.

A dying man is discovered on a beach. A mysterious motorcycle rider takes the man's identification and speeds off. The man has bubonic plague. Five-O races to contain a potential plague outbreak and discover what the motorcycle rider is doing. McGarrett & Co. uncover a plot by a Chinese operative to steal a U.S. night-vision device under development at a U.S. military base in Hawaii.

In Oahu State Prison, cons led by Big Chicken want to bring Swanson to heel because he doesn't show enough respect for "the system." But Swanson manages to shoot one of his attackers with guns the cons had smuggled into the prison. Swanson gathers up prison guards as hostages to try to get out of the prison. Swanson says if he's not let out, he'll start killing the hostages. McGarrett offers himself up as a hostage to try to head off bloodshed.

McGarrett receives a cryptic letter and a photo of a woman with an "x" drawn through it. The woman was stabbed repeatedly. Later, another is killed the same way and Five-O gets another letter. The victims both worked at the same company, Hawaiian Amalgamated Industries. The company is headed by the headstrong Martha, who employs two nephews, Arnold and Charlie. The killings are a ruse, intended to create the impression of a psychopath killer on the loose. In reality, the killer is Charlie and he kills Martha so he can inherit his share of her estate. He also stabs himself to make it appear he was a target of an attack. But Martha's will has Arnold take over running the company and a relatively modest trust for Charlie. The development spurs Charlie to try to kill Arnold and frame him for the killings.

Joey Kalama, son of police detective Phil Kalama, nearly goes down in a boxing match then comes back to win the fight. Later, he is beaten by two thugs and dies. McGarrett & Co. investigate the death while trying to rein in Phil, who is also probing the case. The heat is turned up on Five-O after Joey's manager falls to his death accidentally while Phil was trying to question him.

McGarrett's sister, whose infant son is dying of cancer, has fallen under the sway of a medical quack. Her husband is afraid to confront her. Instead, he summons McGarrett to their home in Los Angeles. McGarrett enlists the aid of U.S. Food and Drug Administration officials in prosecuting the quack. However, McGarrett's sister refuses to believe her big brother. When the child dies, the sister turns against McGarrett. As the trial begins, it is disrupted by followers of the quack.

McGarrett, desperate to convict medical quack C.L. Fremont, seeks evidence where she can be prosecuted for a more serious charge. Facing extremely long odds, he convinces the family of a former Fremont patient to have the body exhumed. However, the casket wasn't airtight. McGarrett and Zipser, an attorney for the U.S. Food and Drug Administration, instead manage to trip up Fremont in court. The maneuver causes McGarrett's sister to realize her brother had been right all along.

The leader of a band of protesters is killed while confronting the general of a foreign nation. Authorities initially believe it was an assassination attempt on the general's life. Five-O, however, turns up leads that the lead protester was the intended victim of the killer. McGarrett & Co. probe the backgrounds of the other protesters. While the young people protested for peace, it turns out some of them did have motive.

Five-O intercepts a "box man," an expert safe cracker, at the Honolulu airport. The criminal is killed by a shot from Dan Williams, who fired just before the criminal would have shot Chin Ho. The man had $20,000 and instructions to check into a hotel on Hilo. McGarrett goes undercover, posing as the box man. The lawman finds himself involved in a conspiracy involving two other criminals, Swanson and Andre, as well as a woman. All claim to know nothing about "the Man" who is sending them instructions. Eventually, McGarrett discovers the target of the plot -- a yacht where a diplomat of another nation is staying which has six kilos of heroin in a very secure safe. (This episode apparently takes place before episode 1.16, "The Box," where Swanson appears as an inmate in Oahu State Prison.)

At the request of the Governor, McGarrett investigates recent odd behavior by Sam Kalakua. Sam, a friend of the Governor's and a distant relative of Kono's, is also among the last of descendants of Hawaiian kings. Sam says he saw the Hawaiian goddess of fire, Pele coming for him and fired a gun in defense. McGarrett ("I'm a man of this century") doesn't believe in Hawaiian gods but also thinks that Sam is not senile or imagining things. Sam's closest relative is his nephew George, who is married to Eleanor, who yearns for a jet set life. The couple are aligned with a real estate developer who has designs on Sam's estate and a film maker who's an expert in special effects. When she can't get Sam committed to a mental institution, Eleanor decides it's time to kill Sam.

The series pilot, which originally aired as a two-hour TV movie, is re-edited as a two-part episode of the series. In the opening installment, a U.S. intelligent agent, a friend of McGarrett's, turns up dead on a Honolulu beach. McGarrett, knowing the man didn't swim, decides to investigate the death as a homicide. Five-O gets no cooperation from the Feds, making McGarrett suspicious. His probe eventually leads to a mysterious ship, which is in dock for repairs. Going undercover as a member of a repair crew, McGarrett discovers a futuristic-looking chamber.

McGarrett goes to the Governor with news of what he's uncovered in his investigation. The two agree the matter is too big for any state or local law-enforcement agency. The Governor contacts Jonathan Kaye, who oversees U.S. intelligence activity in the Pacific Rim. Kaye recruits McGarrett as part of a risky operation. The lawman will be programmed to impart false information under interrogation -- and U.S. intelligence will leak word that McGarrett knows the identity of "Control," the man who has direct supervision of U.S. agents in the region. McGarrett, as planned, is captured and subjected to Wo Fat's "cocoon." He also uncovers the traitor who has been helping Wo Fat.