McGarrett refuses to listen to Danny's pleas to take it easy while recovering from surgery; Five-0 goes on the hunt for a serial killer as fear grows that it's not safe to travel to 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 killer vigilante.
FBI profiler Alicia Brown is forced to join McGarrett in the hunt for the chess-piece killer when she finds a body in her bed. Meanwhile, Kono reconnects with a former surfing competitor who is now a disabled and homeless war veteran.
Five-0 must find McGarrett and Alicia when they are kidnapped by the serial killer 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 statement on gun violence.
On Halloween, Five-0 investigates the murder of a medium with a checkered past who was apparently scared to death by a poltergeist. Also, Kono and Adam are kidnapped by what appears to be a death cult.
Catherine informs Five-0 that McGarrett's mother has been captured and is in danger of being executed for trying to free Wo Fat's imprisoned father; Also, Chin loses his appeal to have Sara's adoption delayed, and she must move to Mexico.
While Danny chaperones Grace's winter formal, 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.
When a conspiracy theorist with compelling evidence that JFK's cabinet ordered his assassination is murdered, Five-0 investigate's one of history's most notorious 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 murder. 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.
Five-0 races to Mexico where Chin puts his life on the line after his niece Sara is kidnapped.
Chin is kidnapped by a cartel in Mexico and Five-0 races to rescue him before he is executed by his vengeful abductors. Meanwhile, Grover goes undercover as a car salesman to investigate a murder that turns out to be far more complex and dangerous than expected.
As Max prepares to say goodbye to his Five-0 ohana, they must investigate a murder during a police convention on the island.
The team faces a contentious U.S. Marshal after a murder suspect escapes capture and looks for asylum in the sovereign land that belongs to the Nation of Hawaii.
When working a murder 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 leprosy colony in Hawaii.
While McGarrett and Danno celebrate Valentine's Day with their girlfriends, the rest of Five-0 investigates the murder 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 killer 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 murder 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 murder 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 their most dangerous rescue yet of young girls trapped in the sex trafficking ring they have been tracking this year. Also, Kono, deeply affected by the case, makes a life-changing decision.
