(Hunting Monsters) McGarrett and Five-0 once again become entangled in the twisted mind games of serial killer Dr. Madison Gray (Elizabeth Röhm) when she stumbles into HPD covered in blood that matches Alicia Brown's (Claire Forlani), and claims amnesia.
(Crazy In Love) 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.
(Big Game) 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 leper colony in Hawaii.
(The Clouds Always Return to Awalua) As Max prepares to say goodbye to his Five-0 ohana, they must investigate a murder during a police convention on the Island.
(The Deal) The team handles the fallout in Mexico after Chins problems, back on the Island Grover goes undercover and things get hot.
(Snatchback) Five-0 races to Mexico where Chin puts his life on the line after his niece Sara is kidnapped.
(The Burden) 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 (guest star Missy Peregrym), visits Oahu for a business conference, and he suspects that she may be getting too close to a co-worker.
(Two Days in November) A conspiracy theorist with compelling evidence that JFK's cabinet ordered his assassination is murdered. Five-0 investigates and delves into one of history's most fascinating unsolved mysteries.
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.
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.
The murder 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.
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,
Five-0 must find McGarrett and Alicia when they are kidnapped by the serial killer they’ve been hunting,
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 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.
When the bodies of two serial killers 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.