The son of the baseball player becomes the vital witness in a murder, but he is reluctant to tell either his father or Five-O of the crime.

A baseball player, Lon Phillips, brings his backward son to Hawaii to escape threats on his life on the mainland.

Danno's past comes back to haunt him when the brother of a young boy he shot is released and wants revenge. The brother takes Chin Ho, Jenny and others hostage in McGarrett's office and threatens to blow them up, and Danno must resolve the tense situation.

The wife of a convicted man fakes evidence in a new crime so that McGarrett will have to re-open her husband's case.

The wife of an arms dealer is kidnapped by revolutionaries who want the guns diverted from their original destination, but the arms dealer himself is not as innocent as matters would indicate.

Five-O must deal with treason, murder and double-crosses in order to solve the case and prevent the U.S. from being flooded by fake currency.

Wo Fat and other top international agents converge on Hawaii to place bids on printing plates for twenty dollar bills, which are in the possession of a former friend of McGarrett.

Five-O investigates the death of Vietnam hero Jack Rigney, who fell from a balcony. His father is a World War II veteran, but his brother Michael is a peacenik, and Danno goes undercover as a draft dodger to help solve the mystery of Jack's death.

An electronics genius is busted out of prison so he can mastermind a massive robbery of diamonds from the Honolulu Diamond Exchange.

A cowboy fears the loss of his land to a crooked estate agent and accidentally kills him by hitting him. McGarrett and his team must track the cowboy into the mountains and persuade him to give himself up.

When a convicted murderer, Harry Kellem, hears a dying man say he committed the crime that Kellem was jailed for, he takes a doctor hostage and McGarrett must negotiate his way out of the situation.

McGarrett must apprehend two abductors who are on the run with the proceeds of their crime in order to protect the lives of their co-conspirators.

Dan Williams's fiancée is murdered by a strangler who writes poetry in lipstick on his victims' legs. Danno resolves to catch the culprit who has other murderous plans to carry out.

McGarrett and company must pit their wits against a veteran thief and robber who leaves Monopoly money at the scene of his crimes.

Five-O search for the criminals who have set up Hawaiian singer and ecologist Jimmy Nuanu as the fall guy for a sewage plant bombing.

The hitman sent to kill the witness to a two year old murder instead falls in love with her and McGarrett and the team must lead the search to find her before duty overtakes love.

A Japanese computer research company executive is recognized by a veteran as his former captor in a Phillippine prison camp in World War II.

When a ruthless businessman is blown up in a boat explosion, Five-O has many suspects to choose from, and they use psychological methods to determine the guilty party.

Five-O's efforts to rescue a young boy from kidnappers go wrong when Kono is captured and beaten. An angry McGarrett must work out a way to rescue Kono without further endangering him.

Shortly after giving a recital, the violin of a visiting Russian virtuoso is stolen, and McGarrett must retrieve it before the theft turns into an international incident.

When a lawyer is murdered, his wife becomes the top suspect and McGarrett investigates. However, matters are complicated by the fact that the woman had a relationship with McGarrett, and he jeopardizes his job because of this.

Dr. Lemira, an opposition leader for Greece, is living in exile in Hawaii, but Klaus Marberg is sent to assassinate him. His plan is to get himself shot and work his way into Dr. Lemira's confidence so he can kill him easily. McGarrett must work out this plot and save the day before it is too late.

Singer Eadie Jordan has not only a comeback concert to perform, but also a serious heroin addiction. Poisoned heroin is being peddled on the islands, and McGarrett must try to save Eadie from scoring for the last time.

Five-O must act swiftly when the daughter of a top neurosurgeon is kidnapped by Wo Fat in order to make the surgeon operate on a wounded U.S. undercover agent who is carrying secret information of use to the Chinese.