Following McGarrett and Wo Fat's escape, gunmen hit Five-0 headquarters; McGarrett must turn on his own in order to find Catherine.
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.
When a missing artifact seems to be the key to solving a double murder, a conspiracy theorist (Jorge Garcia) helps the team.
When a wedding crasher is murdered, a runaway bride is the prime suspect; Danny makes a decision about his relationship with Gabby.
A seemingly harmless surveillance job turns deadly; in hope of saving Kono, Adam considers making a sacrifice.
When a zombielike man is shot, the team members are led to a madman who is performing experiments on humans.
When Mary gets sick, McGarrett and the team must watch her newly adopted baby while they investigate the murder of an undercover ATF agent.
The governor asks McGarrett and Grover to serve a warrant to a young computer hacker (Nick Jonas) in order to protect national security.
A secret service agent is murdered while the president is traveling to Oahu; as Thanksgiving approaches, McGarrett's Aunt Deb (Carol Burnett) visits and shares a stunning secret.
An attempted murder leads the team to investigate a deadly crime committed in Hawaii during World War II.
An investigation involving a potential serial killer puts Chin's life in danger; Grace and Danny find a mysterious puzzle box.
One of Grover's friends disappears after apparently committing a murder.
Chin is questioned about his father's murder and how his relationship with Malia and her family could have adversely affected the investigation.
An escaped convict who wants Five-0 to prove his innocence abducts Danny and McGarrett; Grace punches a person at school.
The team investigates the death of a real estate agent whose body was found in the walls of one of his listings; Danny's mother visits with unexpected news.
A triple homicide is linked to a secret, downed Chinese satellite; Danny's mother goes on a ride-along with Grover.
A man is shot as his daughter is abducted; Danny tries to reunite his parents; Jerry finds a code on McGarrett's champ box.
The daughter of a macadamia nut tycoon is killed with a stiletto heel during Chin's high school reunion.
Danny and McGarrett are trapped inside an abandoned building rigged to explode.
A murder investigation leads the team to uncover a possible terrorist cell planning an attack on U.S. soil.
Catherine and McGarrett go to Afghanistan to help a young boy, whose family saved Catherine years earlier.