When a list of undercover CIA agents is stolen, Steve and Five-0 enlist the help of Magnum, Higgins, Rick and TC to get it back and protect national security. Also, Higgins gives Tani some personal advice.
Five-0 investigates a tourist helicopter that was shot down by a missile. They trace the stolen artillery to a ghost from McGarrett's past, Wo Fat. Also, after Adam's ordeal in rescuing Tamiko and reconnecting with the Yakuza, he makes a bold decision about his future with Five-0.
When Adam's girlfriend, Tamiko, is kidnapped right in front of him, he shuts out Five-0 and breaks all the rules in order to get her back. Also, Five-0 investigates three seemingly unconnected homicides.
It's Thanksgiving, and while Junior and Tani track down the thief who robbed his parents' home, Five-0 investigates the murder of a beloved philanthropist and the theft of his ultra-valuable koa tree. Also, Danny moves in with McGarrett.
Five-0 teams up with a DEA agent to search for a killer whose plane crashed in the jungle with $10 million worth of heroin on board. Also, Grover is thrilled when his niece Siobhan comes to try out for the University of Hawaii basketball team.
The CIA informs McGarrett that his mother has gone rogue on her undercover mission and may have killed her partner. Steve decides to go solo to Mexico in order to bring her home and prove her innocence.
McGarrett and the team investigate when a deadly hit-and-run involves a driverless car carrying heroin, and what could be a new means for delivering drugs. Also, Tani and Quinn are stuck with a pair of YouTubers who are brought on a ride-along with Five-0.
Five-0 investigates when a plane that mysteriously crashed into the Pacific in the '80s is found, but with a recently murdered scuba diver inside. Also, as MacGarrett and Quinn zero in on who planted the bomb in his garage.
Tani and Junior must plot an escape for themselves and several civilians after they become trapped inside a deadly tunnel collapse, while Five-0 investigates the cause and culprits of the cave-in. Also, Eddie the dog uses his field experience and sniffs out a bomb that has been planted in McGarrett's home