Five-0 investigates the hijacking of a delivery truck in which the driver is killed, Danny's ex-wife goes into labor, and both Steve and the Yakuza put pressure on Joe to give answers.
A woman is murdered during the governor's fund raising dinner, and Five-0 gets in trouble with the governor when the team goes too far trying to catch the killer.
While Steve's sister Mary accidentally gets caught in the middle of a plot to smuggle conflict diamonds, Five-0 and HPD get the help of an elderly ex-con recently released from prison to find the smugglers.
Just as McGarrett finally gets his hands on his arch nemesis Wo Fat in a special ops raid, he's blindsided when he finds that the Japanese Yakuza is hot on their trail and wants them both dead.
Five-0 needs the help of an imprisoned dirty cop to track down a suspect who killed Captain Fryer and set off a bomb in the HPD. Meanwhile, Joe White returns and promises to reveal Shelbourne's identity to McGarrett.
McGarrett brings his mother back to the island. But her life may be in danger after Wo Fat escapes from prison with the help of an unlikely partner: Frank Delano.
Five-0 discovers a terrorist cell on the island; Danny has a flashback to one of the most eventful days of his time as a Newark police officer in 2001.
McGarrett is convinced that a psychiatrist murdered one of her patients, but will she get the last laugh? Meanwhile, Catherine discovers that an assassin is on the island and is looking for Doris McGarrett.
McGarrett discovers that a botched bank robbery actually wasn't about the money, while Danny protects a Victoria's Secret supermodel who has been threatened by a stalker.
McGarrett and a young girl are held hostage by a diamond thief during a campout, and Kono's boyfriend, Adam, welcomes his brother back from prison and gives him an offer to become a legitimate businessman.