When investigating a deserted yacht adrift at sea, McGarrett, Danny, Tani and Junior are exposed to a deadly bioweapon and the rest of Five-0 have only eight hours to find an antidote.

McGarrett poses as a pilot to investigate a plane crash that led to the death of a pilot in an air race.

Junior and Adam back up McGarrett when a bank heist in progress forces Steve to make a potentially heartbreaking mistake. Also, Adam is forced to face an empty home without Kono

The murder of two tourists leads Five-0 to a man suffering from multiple personality disorder, where one of them becomes violent and another is a child. McGarrett is accompanied on the case by a stress management consultant, whom Danny and the others have hired to help him manage his health.

At Halloween, Five-0 must investigate a string of murders that mirror stories from well-known Hawaiian folklore. Also, Grover is called to visit a man hours away from execution who may hold the key to a case that has plagued Grover for years.

The lives of Five-0’s informants are in danger when the HPD system is hacked and one ends up dead, forcing McGarrett to enlist the help of hacker Aaron Wright (Joey Lawrence), who he just imprisoned

Five-0 enlists the help of an old friend when the boss of a major crime family is murdered, triggering revenge killings across the island. Also, MacGarrett and Danny begin sorting out particulars in their new restaurant venture,

McGarrett and Five-0 work with an injured police dog who is the only witness to an ambushed drug bust. Also, McGarrett is visited by Junior Reigns, a former SEAL, who is looking to join the task force.

McGarrett and Danny recruit Tani Rey to join the task force when diabolical hacker Aaron Wright releases a dangerous arsonist from prison.

McGarrett risks his life when Five-0 attempts their most dangerous rescue yet of young girls trapped in the sex trafficking ring they have been tracking this year. Also, Kono, deeply affected by the case, makes a life-changing decision.