The team discovers a Russian spy ring hiding on Oahu when a Russian submarine appears off the coast.
Hawaii Five-0 episode guide
Ka Lala Kaukonakona Haki 'Ole I Ka Pa A Ka Makani Kona (The Tough Branch That Does Not Break in the Kona Glae
McGarrett joins Junior and his SEAL team on a mission to capture an elusive person who is holding his mentor hostage; Gerard Hirsch and Kamekona help Grover and Tani on a murder case involving art stolen by Nazis during World War II.
McGarrett and Five-0 take on the mob when a former boss is killed; Junior's friend is on the run after witnessing the murder.
Duke is forced to steal crucial evidence from the police locker in exchange for his kidnapped granddaughter; Jerry goes under cover at a mental health facility to solve a murder.
Harry Langford enlists McGarrett and Danny's help to track down a teenage British royal who has run away while under his protection; Grover, Tani and Junior work a 25-year-old murder case after a mysterious videotape arrives at headquarters.
Catherine Rollins recruits McGarrett and Jerry to help track down uranium thought to be hidden on an abandoned Hawaiian island before a terrorist makes dirty bombs with it; Junior gets trapped in a ravine.
Aohe Mea Make I Ka Hewa; Make No I Ka Mihi Ole No One Has Ever Died for the Mistakes he Has Made; Only Because he Didn’t
A hit man McGarrett's father failed to arrest comes to McGarrett to finally confess his crimes and admit where he buried his victims; Jessie makes a dangerous decision that could ruin Adam's life.
The ex-wife of the man who shot Danny reveals how Danny helped save her life; Tani and Junior are assigned to walk the beat as uniformed officers for the day; Adam is framed for the murder of the crime boss he has been tracking.
Adam's mission to take down organized crime goes sideways when the bait he uses falls into the wrong hands; Adam begins to doubt Jessie's allegiance.
Tani and Junior go under cover as prospective parents to infiltrate a private school where the headmaster was murdered; Adam's life is on the line when he is held captive and forced to produce a massive amount of money.
McGarrett and Danny investigate the murder of a private detective whose client was killed the same way; Adam sends Jessie into a dangerous situation with disastrous consequences; Danny's uncle comes to town to help with the restaurant.
The corpse of a diamond smuggler is stolen from a graveyard; Five-0 tracks down his partner, who is determined to retrieve their latest batch of contraband; Adam recruits a new, confidential informant; Tani gets a devastating call.
Mac participates in a challenge to create robotic combat machines; Mac must help a competitor when her vehicle is hacked and heads for the Pentagon; Jack attends his high school reunion.
When an FBI agent who was cracking down on organized crime is killed, McGarrett rounds up every gang-related criminal on the island to find the culprit responsible for the murder.
The murder of two tourists leads the team to a man who has multiple personality disorder; Danny and the others hire a stress management consultant to help McGarrett.
At Halloween, the team investigates a string of murders that mirrors stories from well-known Hawaiian folklore; Grover visits a man who is hours away from execution and may hold the key to a case that has plagued Grover for years.
E Uhi Wale No 'A'Ole E Nalo, He Imu Puhi (No Matter How Much One Covers A Steaming Imu, The Smoke Will Rise)
When the HPD system is hacked and one of the Five-0's informants ends up dead, McGarrett enlists the help of hacker Aaron Wright, whom he just imprisoned.
The team enlists an old friend when a crime boss is murdered, triggering revenge killings across the island; MacGarrett and Danny work out details concerning their new restaurant venture.
McGarrett and the team work with an injured police dog that is the only witness to an ambushed drug bust; a former SEAL looks to join the task force.
McGarrett and Danny recruit Tani Rey to join the task force when a hacker releases a dangerous arsonist from prison.