The sixth season of Hawaii Five-0 premiered on September 25, 2015 on CBS and concluded on May 13, 2016. The season consisted of 25 episodes.
Episode 1 – Do Not Disturb the Water That is Tranquil
Season 6 begins with Five-0 investigating a centuries-old Oahu palace raid involving pirates, buried treasure and a killer who is using a stolen painting as a map. Meanwhile, Kono and Adam are threatened and tortured by Gabriel and Danny shows concern for Steve regarding Catherine’s return to the island.
Episode 2 – Ashes to Ashes
A bomb squad is attacked and the culprit threatens to detonate additional explosive unless arsonist Jason Duclair is released from prison. Meanwhile, Adam returns from the hospital and Kono realizes they are being watched; and McGarrett prepares to take his relationship with Catherine to the next level.
Episode 3 – The Chillin Storm is on the Mountain
Five-0 investigates the death of a scuba diver who was killed with a gun found on the ocean floor that was used recently in another murder. Meanwhile, McGarrett prepares to propose to Catherine.
Episode 4 – Best Laid Plans
Five-0 investigates the death of a wealthy recluse who is found dead in a remote field with nearly one million dollars in counterfeit bills. Meanwhile, Adam is kidnapped by the Yakuza and is forced to torture one of Gabriel’s men.
Episode 5 – Big Lie
Five-0 interrogates members of a stunt biker gang to locate a killer who escaped by jumping his motorcycle from one rooftop to another. Meanwhile, the riders prepare to race in a Tough Mudder competition.
Episode 6 – Monsters
On Halloween, Five-0 needs to track down a serial killer inspired by Frankenstein. Jerry asks the team for help when an armed gang raids a blood bank. When Grace lies and sneaks out to a Halloween party, Danny heads out to track her down.
Episode 7 – Day Trippers
Steve’s first date with Lynn goes awry when the deserted island he chose for their date turns out to be the same island a mob boss is hiding on – and he’ll do anything to keep his location a secret. Five-0 must find the father of a high school football star who will be murdered by a local gambler if his son doesn’t throw the big game.
Episode 8 – The Artful Dodger
Five-0 works with a charming con man to find a killer, after his female partner is murdered on the job. Meanwhile, San Francisco police inspector Abby Dunn helps Chin investigate the murders of five Chinese arm dealers.
Episode 9 – Charade
Five-0 goes back to school when a college professor is killed and Danny goes undercover as his replacement.
Episode 10 – The Sweet Science
The brother of a promising local boxer is murdered and the chief suspect is the outspoken reigning champion opponent from the mainland.
Episode 11- One’s Personal Sense of Responsibility
McGarrett and Danny attend a couples retreat in Maui to work on their partnership issues. Meanwhile, Kamakona’s dangerous past comes back to haunt him.
Episode 12 – Love Give Life Within
McGarrett’s Aunt Deb visits Oahu on a very personal mission. Meanwhile, Five-0 investigates when some unstable Japanese World War II bombs left behind on the island are stolen.
Episode 13 – Hold the Breath
Grover travels to Chicago to finally get a confession from his old friend Clay Maxwell about why he killed his own wife. Meanwhile, Chin and Kono accidentally stumble upon two killers who hold them at gunpoint and have no idea they are cops.
Episode 14- Misery Loves Company
As Five-0 investigates a double homicide involving marital infidelity, McGarrett and his team recall their disastrous Valentine’s Day experiences.
Episode 15 – The Good Soldier
Danny’s mother is questioned by the FBI. Meanwhile, McGarrett partners with a young man with autism who may have information that could solve the murder of the man’s only friend.
Episode 16 – The Solid Cornerstone
Sang Min, Five-0’s sketchy longtime confidential informant, is accused of murder, so McGarrett asks his old friend Odell Martin to defend him.
Episode 17 – Assets
McGarrett and Five-0 must track down a Russian spy who has stolen a flash drive containing classified NSA information that puts the life of a member of their Ohana at risk. Also, McGarrett finally learns why Catherine left him, and Abby continues to conceal her actual mission from Chin and Five-0.
Episode 18 – The Hunter
Five-0 uncovers a deadly slave trade operating aboard an illegal fishing vessel after a man is found left for dead drifting off the coast of Oahu. Meanwhile, Danny’s car is stolen while he is out with his kids and he commandeers a bus to chase down the thieves.
Episode 19 – Care for Ones People
A case from 15 years ago forces Grover to take his family on the run when a dangerous mob boss tracks him down to seek revenge.
Episode 20 – Rampage
Five-0 investigates the theft of a high-tech, indestructible suit created for the U.S. military. Meanwhile, Jerry tries to help his sister save a captive elephant.
Episode 21 – The Cost of Freedom
Five-0 goes on a manhunt when a chemical spill permits six dangerous inmates to escape, including Kono’s husband, Adam.
Episode 22 – For the World to Know
Five-0 tries to save a kidnapped college student from a dangerous vigilante. Meanwhile, Max, Kamekona and Flippa fight to survive after being shipwrecked.
Episode 23 – Blood Ties
A woman is murdered in her home and Five-0 learns that one of their own has a deep connection to the victim’s young daughter.
Episode 24 – The Entrance is Stopped with a Spider’s Web
Five-0 gets trapped inside a dilapidated building in Oahu’s Chinatown, where they try to protect a wounded Gabriel and plan their escape. But gunmen looking to kill Gabriel storm the building.
Episode 25 – My Desire is Only for the Chief
Season 6 ends with McGarrett and Danny working undercover as drug pilots to stop a meth epidemic on the island. When McGarrett is seriously wounded, Danny is forced to break their cover and land the plane in order to save his partner’s life.
Another season full of comedy and action but this time things are getting far more personal for Kono, Steve, Chin Ho, Lou and Danny.