The team members go under cover on a cruise ship in order to locate and disable stolen rockets as Valentine's Day approaches, Ralph develops a crush.
The team must help an injured former Secret Service agent regain his memory in order to stop the launching of weapons of mass destruction.
The team searches for a CIA mole who has been coerced into stealing deadly chemicals Paige shows Walter how to flirt.
The team tries to help Ralph when he is taken by the FBI for questioning after his web game play unintentionally reveals a CIA safe house's location.
Chin is questioned about his father's murder and how his relationship with Malia and her family could have adversely affected the investigation.
One of Grover's friends disappears after apparently committing a murder.
When a zombielike man is shot, the team members are led to a madman who is performing experiments on humans.
A seemingly harmless surveillance job turns deadly in hope of saving Kono, Adam considers making a sacrifice.
When a wedding crasher is murdered, a runaway bride is the prime suspect Danny makes a decision about his relationship with Gabby.
When a missing artifact seems to be the key to solving a double murder, a conspiracy theorist (Jorge Garcia) helps the team.
As the Five-0 team members investigate a murder, they are led to a Texas ranger (Tim Daly) who came to Hawaii to look for his daughter Adam and Kono fight to stay alive.
Following McGarrett and Wo Fat's escape, gunmen hit Five-0 headquarters McGarrett must turn on his own in order to find Catherine.
Kono is blamed for a murder she did not commit McGarrett's visit to Wo Fat leads to a shocking discovery.
A petty officer's murder leads the team to a night club where Pride's mother used to perform Lasalle must return home to Alabama after receiving an unexpected call from his family.
Sebastian's high school friend asks for help when her business partner is killed at a gaming convention FBI Special Agent Raymond Isler believes Adrian is the hacker that the Cyber Crimes division has been tracking for years.
After a deadly armed robbery and high-speed chase is linked to an undercover ATF operation, Percy reconnects with her former ATF partner.
Rita Deveraux tells Pride that Douglas Hamilton is about to make a deal to get out of prison Pride and the team re-investigate the Clearwater case in hopes of spoiling his plans.
Pride starts to doubt evidence suggesting homeless kids murdered a petty officer.
When Dr. Brennan uncovers the identity of a man killed while driving a car registered to a prominent Middle Eastern man with ties to the U.S. government, she and Booth find themselves tracking a terrorist.
Skeletal remains found at the bottom of a lake turn out to be those of a congressman's former aide.