In the season premiere episode, McGarrett and Wo Fat make a narrow escape from maximum security, gunman storm Five-0 headquarters and Catherine is taken hostage. Now, in McGarrett’s quest to save Catherine, he must break the rules and go head-to-head with new SWAT Commander Captain Grover (Chi McBride). Meanwhile, Kono and Adam’s secret location in Hong Kong is compromised.
A Texas Ranger comes to the island to find his missing daughter, and the Five-0 team gets involved when murder happens. Meanwhile, Kono and Adam's hidden location.
A double murder forces the Five-0 team to bring in a conspiracy theorist to help them find a missing artifact tied to the killings.
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.
Songs: Doolin Rakes
-- Molly Malone, Hawaii Five-0 Cast -- The Minstrel Boy
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.
-- Mess Around, The Rocky Horror Picture Show Movie Cast -- Time Warp, Enrique Iglesias
-- Turn the Night Up, Avicii
-- You Make Me
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. Nick Jonas guest stars as the young computer hacker.
As Thanksgiving approaches, Five -0 investigates the murder of a secret service agent just as the president travels to O'ahu. Also McGarrett's Aunt Deb visits, bringing with her a shocking secret.
The attempted murder of a Pearl Harbor veteran leads Five-0 to investigate a deadley crime committed within the interment camps on O'ahu 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.