A man is found dead after having been robbed by a motorcyclist with a gun, and McGarrett is shocked to discover that the man was suffering from bubonic plague. The islands are quarantined, and the team must follow a series of clues to discover the cause of the outbreak.

A tsunami warning is called and a geneticist is evacuated from a conference. He is then kidnapped under the orders of Wo Fat, but he uses his diabetic medical condition as a ploy to stop Wo Fat from carrying out the plan to return him to China.

McGarrett must counter a threat by international terrorist Erich Stoss to use a fungus to wipe out Hawaii's sugar cane, half of the world's supply.

McGarrett gets a phone call from Singapore and goes to rescue Nicole Wylie, a witness who has changed her mind and wants to testify. However, the pair must face many dangers on their return trip back to Hawaii.

When a young son of a businessman escapes from captivity by ‘The Devil' and ‘Mr. Frog', Five-O must recover the $300,000 ransom money that the desperate father paid.

Peter Corman is murdered during a game of poker, and his brother Lorenzo arrives in Hawaii for revenge. McGarrett must work out what happened and prevent Lorenzo from carrying out his intentions.