The team hunts for a murderer who has been targeting serial killers, marking their corpses with an ivory chess piece.
A rogue MI-6 agent is the key to finding a terrorist who plans to cause the meltdown of nuclear reactors across Europe; McGarrett and Danny need the help of an FBI profiler to find a killer.
After finding a corpse in her bed, FBI profiler Alicia Brown joins McGarrett in a hunt for a killer; Kono reconnects with a former surfing competitor.
When the serial killer that Alicia and McGarrett have been hunting kidnaps them, it's up to Five-0 to find them before it's too late.
A cache of guns is stolen by a person looking to make a statement on gun violence; Kono and Adam are reunited.
On Halloween, the team investigates the murder of a medium who was apparently frightened to death by a poltergeist; a mysterious death cult kidnaps Kono and Adam.
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; Chin is unable to delay Sara's adoption.
While Danny chaperones Grace's high school dance, the venue is seized by terrorists, who hold everyone hostage with the intent of abducting a diplomat's son; Danny and Grover discover that Will is Grace's secret boyfriend.
A conspiracy theorist with compelling information that JFK's own cabinet planned his assassination is murdered.
A boy suffering from PTSD undergoes hypnosis and realizes he may have witnessed a murder related to a 10-year-old cold case; Danny's sister visits Oahu.
The team rushes to Mexico, where Chin puts his life in jeopardy in an effort to rescue Sara, his kidnapped niece.
When Chin is kidnapped by a Mexican cartel, Five-0 must rescue him before he is executed by the vengeful group; Grover goes under cover to investigate a murder, which turns out to be far more complex and dangerous than anticipated.
While Max prepares to say his goodbyes, the team investigates a murder during a police convention on the island.
The team faces a contentious U.S. Marshall after a murder suspect escapes capture and looks for asylum in the sovereign land that belongs to the Nation of Hawaii.
While working a murder case, Five-0 discovers 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 Five-0 team investigates the murder of a man taking a class on how to meet women.
The Five-0 must once again engage in the twisted mind games of serial killer Dr. Madison Gray when she arrives at the HPD covered in blood that matches Alicia Brown's.
After tracking down the missing uranium, which has been used to build a bomb in the middle of the jungle, McGarrett and Danny must move the explosive material 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; Chin and Grover investigate a murder at a sober living facility.
The Five-0 helps a private investigator in the case of a kidnapped woman whose husband may have something to hide; Rachel tells Danny that she is getting a divorce from Stan.
McGarrett and the Five-0 are captured while tracking a dangerous nemesis to the island of Lanai; Grover takes his son to Chicago, where he testifies against a dirty cop.
McGarrett works the murder case of one of the last survivors of the USS Arizona; Adam uncovers bone fragments at his new construction job.
Danny protects a coma patient who was the key witness from his last case at the Hawaiian Police Department.
McGarrett gets a tip that someone is plotting a terror attack on Oahu; Chin and Abby face a difficult decision.