Five-0 is baffled when a highly skilled ring of thieves pulls off a heist of an armored car, killing two security guards but leaving the money behind. Their only lead in the case requires Danny to reluctantly ask his ex-wife for a favor.

After a high-speed chase, the team makes a gruesome discovery; Chin Ho and his ex-fiancee are awkwardly reunited.

When the sole witness in a high-profile murder case disappears, Five-0 must head into the jungle to locate and protect her from assassins who are closing in fast.

While Five-0 races to stop a mad bomber before he kills again, Danny gets an unexpected visit from his little brother, Matt, a fun-loving, Wall Street broker. The family reunion is cut short, however, when Danny discovers the real reason that Matt is in Hawaii.

With the invaluable information that was shared by Agent Jenna Kaye, Five-0 is closer than ever to capturing Wo Fat. Their mission takes an abrupt turn, however, when Danny is exposed to a lethal neurological agent that presents an even greater threat: bio-terrorism on the island.

When Five-0 gets too close to the truth about Wo Fat and his associates, the criminal mastermind retaliates by trying to destroy the team. They've always played by their own rules, but when the Governor can no longer protect them, it's time for Five-0 to pay the consequences of their actions.

When Danno and his family are targeted by a vengeful dirty cop from Danno's past, the team steps in to help.

While Five-0 investigates the murder of a bounty hunter after he apprehended a fugitive hiding out in Hawaii, Rachel reveals a long-held secret to Danny that has serious ramifications. Also, as Kono’s wedding nears, Chin voices his concerns to McGarrett that Adam is still working with the Yakuza.

Five-0 helps PI Harry Brown work the case of a kidnapped wealthy woman whose husband may have something to hide. Also, Rachel tells Danny that she is getting a divorce from Stan.