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.
Hawaii Five-0 episode guide
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.