In the wake of his father's murder, Steve McGarrett returns home to Hawaii to find the culprit, only to be offered a chance to head a task force that enjoys immunity from the governor.
When NSA expert Roland Lowery is kidnapped along with his son and one of their own, the team races to find the Serbian gang behind the kidnapping before its leader launches a cyberattack.
When a turf war between two gangs puts the attendees of a football game at risk, Chin Ho is shocked to encounter a familiar face that forces him to confront his past.
When the unit goes after an escaped convict, they learn that he is out to settle an old score with a former acquaintance. Steve takes drastic measures to keep an eye on his sister when she arrives in town.
When the body of an ambassador's daughter is found, the unit finds themselves drawn into the underworld of sex trafficking rings as they seek to uncover what happened to the victim and her sister.
When a crime hits too close to home for Kono, she pours all of her efforts into trying to get to the bottom of what happened, even if it means getting entangled with local gangsters.
As a hostage situation forces the unit to balance their attempt to rescue the hostages and investigate the kidnaper's claim of innocence of murder, Steve receives help from an unlikely source.
When a face from Danny's past is found dead, the investigation takes a personal turn for both Danny and Chin as it involves the same man that destroyed Chin's reputation.
With a tyrannical foreign leader set to arrive in Hawaii, the unit is tasked with foiling a plot to assassinate him, even if they run amok of old friends.
When their investigation into an armed robbery reveals a bigger plot, the unit turns to a familiar face to help them foil the robbers' plans, set to take place during the Honolulu triathlon.
As the unit investigates a case that may have ties to a serial killer, Steve confides in Chin about his father's toolbox, only to discover that the mystery extends to his own mother's death as well.
When Steve discovers that Victor Hesse is still alive, the unit's investigation ends with the life of one of their own in peril, forcing them to take drastic measures to deescalate the situation.
When twin attacks are launched against the McGarrett siblings, Steve pulls out all the stops to get to the bottom of the mystery as his father's investigation of the Yakuza is revealed.
As the unit stumbles into a mystery when a severed head is found in the aftermath of a car chase, their investigation runs into a series of hurdles when the victim's wife goes missing as well.
As a tsunami warning is issued, the unit comes to discover that the warning is tied to a kidnapping and a robbery that ties back to one of their old cases.
As Danny embarks on his own investigation after his ex-wife and daughter are threatened, Steve and Chin work to save the key witness against a drug cartel leader from the assassins sent to silence her.
When a group of pirates kidnaps a number of wealthy college students, it's up to the team to find the kidnappers before dead bodies start dropping.
When suspicious accidents claim the lives of the son of a state judge and a prosecutor, the unit works to find the link between the two men to find the culprit. Danny crosses boundaries in order to help his brother.
Steve gets a warning to back out of his investigation into the Yakuza. The team investigates the murder of a man who seems to have been at the wrong place at the wrong time.
As Steve and Danny stumble on a dead body that leads to the reveal of a bigger plot, Chin finally comes clean about the truth of the incident that tarnished his reputation.
When the wife of an undercover cop is killed, the unit goes after the crime boss he has been undercover with. However, they soon learn that there is more to the case than they thought.
The death of a photographer leads the team to a loan shark, whom Chin is later forced to go to when his uncle's attempt to clear his name leads Chin to make another sacrifice.
As they close in on Wo Fat, Danny's life is put on the line as he gets exposed to sarin, derailing the unit's investigation as they seek to uncover the source of the sarin gas.
When a murder leads Steve to suspect the governor's involvement with Wo Fat, he finds himself framed for a number of crimes he did not do as Wo Fat makes a move against him.