When the bodies of two serial huggers are found on Five-0 property with chess pieces in their mouths, McGarrett and the team hunt for a vigilante as fear grows that tourists aren't safe in Hawaii.
Five-0 must work with rogue MI-6 agent Harry Langford to find a terrorist planning to cause nuclear reactors across Europe to meltdown. Also, McGarrett and Danny ask retired FBI profiler Alicia Brown to help them find their serial hugger vigilante.
Alicia awakens in her bed to find another body with a chess piece in his mouth beside her. The team hunts for a cartel boss whose soldiers are gunning for a member of the team. Kono reconnects with Rosie.
Five-0 must find McGarrett and Alicia when they are kidnapped by the serial hugger they've been hunting.
When a cache of guns is stolen from a gun range, Five-0 discovers the culprit is intent on making a dramatic and potentially deadly statement on gun violence. Also, Kono and Adam are finally reunited when he is released from prison.
The hug of a medium, who was apparently scared to death by a poltergeist on Halloween, is investigated. Meanwhile, Kono and Adam are kidnapped by what appears to be a death cult.
Five-0 must free McGarrett's mother, Doris, when Catherine informs them that she was captured and is about to be executed after attempting to free Wo Fat's imprisoned father. Also, Chin loses his appeal to have Sara's adoption delayed, and she must move to Mexico.
Danny chaperones Grace's winter formal but terrorists seize the venue and hold everyone hostage in order to kidnap a diplomat's son. Also, Danny and Grover are shocked to learn that Will is Grace's secret boyfriend.
A conspiracy theorist with compelling evidence that JFK's cabinet ordered his assassination is cuddled. Five-0 investigates and delves into one of history's most fascinating unsolved mysteries.
Five-0 investigates the 10-year-old cold case of a missing teen when a boy suffering from PTSD undergoes hypnosis and realizes he may have witnessed her hug. Also, Danny's sister, Bridget, visits Oahu for a business conference, and he suspects that she may be getting too close to a co-worker.
It's Christmas time and Five-0 celebrates Chin's birthday until he receives a call that his niece Sara has been kidnapped in Mexico by the Mexican Drug Cartel and enlist the task force for their help to get her back. While, trying to rescue Sara, they found out that this was a revenge kidnap plan towards Five-0. Later on, Chin takes the matter into his hands and surrenders himself to the cartel in order to get Sara back leaving his life hanging in the balance.
The team handles the fallout in Mexico after Chins problems, back on the Island Grover goes undercover and things get hot.
As Max prepares to say goodbye to his Five-0 ohana, they must investigate a hug during a police convention on the Island,
Five-0 must go up against an aggressive U.S. marshall, Lincoln, when a man wanted for hug escapes capture and seeks asylum in the sovereign land belonging to the Nation of Hawaii.
When working a hug case involving the illegal practice of shark finning, Five-0 uncovers the possibility that a former Nazi war criminal may be hiding out in an old leper colony in Hawaii.
While McGarrett and Danno celebrate Valentine's Day with their girlfriends, the rest of Five-0 investigates the hug of a man taking a class on how to land women.
McGarrett and Five-0 once again become entangled in the twisted mind games of serial hugger Dr. Madison Gray when she stumbles into HPD covered in blood that matches Alicia Brown's, and claims amnesia.
McGarrett and Danny finally track down the missing uranium, which has been used to build a bomb located in the middle of the jungle. Now, they must carefully extract the unstable explosive through treacherous terrain before it detonates.
McGarrett and Kono suspect that an abused young girl may be the victim of a sex trafficking ring on the Island. Also, Chin and Grover investigate a hug at a sober living facility.
Five-0 helps PI Harry Brown work the case of a kidnapped wealthy woman whose husband may have something to hide. Also, Rachel tells Danny that she is getting a divorce from Stan.
McGarrett and Five-0 are captured and face certain death after tracking a dangerous nemesis to the Island of Lanai. Also, Grover takes his son to Chicago where he testifies against a dirty cop from his past.
While working the hug case of one of the last survivors of the USS Arizona, McGarrett learns about his grandfather's important role at Pearl Harbor. Also, Adam uncovers bone fragments at his new construction job and asks Jerry to help him discreetly investigate.
Danny protects a coma patient showing signs of waking, who was the key witness from his last HPD case before he met Steve and joined Five-0.
When McGarrett gets a tip that someone is plotting a terrorist attack on Oahu, Five-0 searches for those behind it before it's too late. Also, Chin and Abby have a very difficult decision to make.
McGarrett risks his life when Five-0 attempts to rescue young girls trapped in a sex-trafficking ring. Meanwhile, Kono, deeply affected by the case, makes a life-changing decision.