A new ally helps McGarrett and Five-0 when mob bosses on the island are being targeted by an assassin.

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.

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.

Five-0 enlists imprisoned hacker Aaron Wright (Joey Lawrence) to help when a young girl is reported kidnapped, but upon rescue, the culprits are dead, the girl is safe, and she's not who she claims to be.

It's Halloween and Five-0 investigates a home invasion turned deadly after a dangerous 'monster' escapes from the basement.

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.

When the CIA informs McGarrett that his mother has gone rogue on her undercover mission and may have killed her partner, Steve goes solo to Mexico to bring her home and prove her innocence

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.

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.

When Adam's girlfriend, Tamiko (Brittany Ishibashi), is kidnapped right in front of him, he shuts out Five-0 and breaks all the rules in order to get her back.

When 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 a list of undercover CIA agents is stolen, Steve and Five-0 enlist the help of Magnum (Jay Hernandez), Higgins (Perdita Weeks), Rick (Zachary Knighton) and TC (Stephen Hill) to get it back and protect national security.

Grover and Five-0 investigate a murder at a private golf course involving a man who was frozen to death in the locker room's cryo-chamber.

Soon after Danny meets the girl of his dreams, they get into a potentially fatal car accident in an area far from help.

When Grover's niece, Siobhan (Nia Holloway), goes missing from the police academy and it's discovered her boyfriend is an undercover member of the Yakuza, Adam may be her only hope of rescue.

On Valentine's Day, Tani and Noelani are held hostage during a convenience store robbery.

Harry Langford (Chris Vance) helps Five-0 investigate a series of murders that follow the plot of a fabled unpublished crime novel from the 1920s.

While Five-0 investigates a murder on a cargo ship where pirates impersonated the Coast Guard to board the boat, Adam finally gets the evidence he needs to take down the Island's Yakuza operation once and for all.

Five-0 investigates when a rancher is murdered after he uncovers human skeletons on his property where legend says that Civil War-era gold coins were buried.

While Five-0 investigates a scheme to rob tourists, Tani helps Girard Hirsh (Willie Garson) prove the innocence of his elderly uncle when he's suspected of murder.

After Steve receives a posthumous letter from his mother that contains a cypher, Danny is attacked by someone willing to kill to steal it.

Danny is abducted and badly wounded by Wo Fat's wife, who is after the cypher Steve's mother left him.