Steve McGarrett returns home to Oahu, in order to find his father's killer. The governor offers him the chance to run his own task force (Five-0). Steve's team is joined by Chin Ho Kelly, Danny "Danno" Williams, and Kono Kalakaua.
(Fire Will Never Say that It Has Had Enough) The team investigates a world class hacker who turns out to be the brother of serial hacker Ian Wright, who hacks into the Hawaii State prison and releases serial murderer/arsonist Jason DuClair. He soon begins a massive wildfire. With Kono and Chin on the mainland running their own respective task forces, McGarrett and Danny recruit lifeguard and former Police candidate Tani Rey to join the task force to help out but is reluctant to join. Meanwhile, McGarrett and Danny begin to invest in a restaurant.
(Dog Days) 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.
(Your Knife, My Back. My Gun, Your Head) The team enlists an old friend when a crime boss is murdered, triggering revenge killings across the island; McGarrett and Danny work out details concerning their new restaurant venture.
(No Matter How Much One Covers a Steaming Imu, The Smoke Will Rise) 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.
(At Kama'oma'o, The Land of Activities) 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.
(Unfolded By the Water Are the Faces of the Flowers) 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.
(The Royal Eyes Rest Above) 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.