After McGarrett and Wo Fat narrowly escape from maximum security, gunmen storm Five-0 headquarters, compromising Kono and Adam's secret location in Hong Kong and forcing McGarrett to break the law and turn on his own in order to find a kidnapped Catherine.
Five-0 murder investigation leads the team to help a Texas Ranger who comes to the island to find his missing daughter. Meanwhile, Kono and Adam fight to stay alive when their hidden location is discovered.
Conspiracy theorist helps Five-0 when a missing artifact is the key to solving a double murder.
Five-0 investigates the murder of a wedding crasher, and their prime suspect is the runaway bride. Meanwhile, Danny makes a big decision regarding his relationship with Gabby.
As Catherine's seemingly harmless surveillance job takes a deadly turn, Adam considers making the ultimate sacrifice to save Kono.
When Halloween comes to Hawaii and a zombie-like man is shot, Five-0 races to stop a madman who is conducting experiments on humans.
While working the murder case of an undercover ATF agent, McGarrett and the Five-0 team are tasked with watching Mary's newly adopted baby after she gets sick.
McGarrett and Grover must work together to protect national security after they are tasked by the Governor to serve a warrant to a young computer hacker.
As Thanksgiving approaches, Five -0 investigates the murder of a secret service agent just as the President travels to Oahu. Also, McGarrett's Aunt Deb visits, bringing with her a shocking secret.
The attempted murder of a Pearl Harbor veteran leads Five-0 to use decades old evidence to investigate a deadly crime committed within the internment camps on Oahu during World War II.
Chin's life is put in danger when a murder investigation reveals that the person behind the crime may be a serial killer. Meanwhile, Danny and Grace find a mysterious puzzle box washed up on the shores of Oahu.
McGarrett helps Grover investigate his friend's disappearance after he apparently commits murder. Meanwhile, Kono continues her search for Adam.
Internal Affairs questions Chin about his father's murder 15 years earlier and how his then-new relationship with Malia and her family might have hurt the investigation.
McGarrett and Danny are kidnapped by an escaped convict who wants Five-0 to prove his innocence. Meanwhile, Danny must deal with Grace after she punches someone at school.
While Five-0 investigates the murder of a real estate agent whose body was found in the walls of one of his listings, Danny is thrown when his mother comes to Oahu with shocking news.
Five-0 investigates a triple homicide connected to a downed top-secret Chinese satellite, while Grover takes Danny's mother on a ride-along.
Five-0 aims to uncovers the sordid truth when a girl is taken from her home and her father is shot in the process. Meanwhile, Danny tries to get his parents back together and Jerry deciphers a code he found on the bottom of McGarrett's champ box.
Five-0 investigates when the daughter of a macadamia nut tycoon is murdered with a stiletto heel during Chin's high school reunion.
Five-0 is set up when a bad tip leads them to an abandoned building that is rigged to explode with McGarrett and Danny trapped inside.
The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil.
McGarrett and Catherine travel to Afghanistan to stop the Taliban from harming a young boy whose family saved Catherine's life years ago.
When Grover's daughter is kidnapped by an old nemesis, he is forced to help steal $100 million in order to get her back. Meanwhile, Wo Fat escapes prison and heads back to Oahu.