While Danny chaperones Grace’s winter formal, terrorists seize the venue and hold everyone hostage in order to kidnap a diplomat’s son

When McGarrett gets a tip that someone is plotting a terrorist attack on Oahu, Five-0 searches for those behind it before it’s too late. Also, Chin and Abby have a very difficult decision to make.

McGarrett and Danny recruit Tani Rey to join the task force when diabolical hacker Aaron Wright releases a dangerous arsonist from prison.

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 (Joey Lawrence), who he just imprisoned

It's Christmas Eve and Danny tells Charlie a bedtime story about a recent Five-0 case involving criminals dressed as Santas and a holiday miracle.

A hitman, Leroy Davis, McGarrett’s father failed to arrest comes to McGarrett to finally confess his crimes and admit where he buried his victims. Also, Jessie makes a dangerous decision that could ruin Adam’s life.

Catherine Rollins recruits McGarrett and Jerry to help her track down a uranium deposit thought to be hidden on an abandoned Hawaiian island before a suspected terrorist can make dirty bombs with it. Also, when Junior falls and is trapped in a ravine, he reflects on his estranged relationship with his father.

Harry Five-0 must help Duke after he is forced to steal crucial evidence from the police locker in exchange for his kidnapped granddaughter. Also, Jerry goes undercover at a mental health facility in order to solve a murder.

Crime spikes when a heat wave hits Oahu, causing McGarrett and Danny to hunt down a bank thief, and Tani and Junior's car is stolen while they're on duty. Also, Grover plays the golf game of a lifetime, and Kamekona incites a riot by price-gouging on his shave ice.

McGarrett crosses the line and is arrested while investigating the death of his former SEAL buddy, who died while making an emergency landing on an aircraft carrier, and the only survivor is a baby. Also, Adam returns to Oahu with some devastating news about his marriage.

Adam, Junior and Tani travel to the bottom of the Pacific Ocean when a murder takes place in a remote underwater lab, and the killer may still be on board

As a dangerous hurricane hits Oahu, Five-0 is tasked with protecting El Diablo, a captured serial killer who is being hunted by an assassin. Also, Tani's civilian safety check during the storm turns deadly and Rachel and Charlie evacuate to Danny's house, where the ex-spouses reminisce.

While Adam investigates the murder of an undercover FBI agent about to wed the daughter of a Yakuza leader, Noelani is held hostage and forced, along with her mentor Dr. Chu, to operate at gunpoint on a criminal.

It's Halloween and Five-0 investigates a home invasion turned deadly after a dangerous "monster" escapes from the basement. Also, Max returns to Oahu with a very special guest.

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.

On Valentine's Day, Tani and Noelani are held hostage during a convenience store robbery. Also, Five-0 investigates the hug of a Thai diplomat whose wife confesses to the crime, but Danny suspects she's covering for the real hugger.

While 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, Quinn's former stepdaughter, Olivia, reaches out to her for help after her father doesn't come home.