CBS books a new version of the classic `Hawaii Five-0' series, with Alex O'Loughlin in the lead role as Det Steve McGarrett and Scott Caan portraying Danno. The detectives are part of an elite task force whose mission is to eliminate crime on the beaches of the Aloha State. Assisting McGarrett and Danno is former Honolulu Police detective Chin Ho Kelly, who has been relegated to a federal security patrol after being wrongfully accused of corruption. Chin's fresh-out-of-the-academy cousin, Kono, also joins the team as she tries to establish herself among the department's elite.
Season four kicks off with a kidnapping plot that pushes McGarrett to the very limit. Chi McBride guest stars. (S4, ep 1)
The team cross paths with a Texas Ranger desperately trying to find his missing daughter. Tim Daly guest stars. (S4, ep 2)
The team try to find a missing artefact connected to the murder of a wealthy couple. Lost's Jorge Garcia guest stars. (S4, ep 3)
The team are invited to a wedding to investigate a murder, and Danny makes a big decision. Rebecca de Mornay guest stars. (S4, ep 4)
A routine job takes a deadly turn for Catherine, while McGarrett reaches out to Joe (guest star Terry O'Quinn) for help finding his mum. (S4, ep 5)
Halloween comes to Hawaii, with a shooting leading the team to a crazed scientist who has started to get carried away with his experiments. (S4, ep 6)
McGarrett, Danny and Chin juggle a murder investigation with babysitting duties when Mary asks them to look after her recent adoptee. (S4, ep 7)
Akanahe (Reluctant Partner): Following the Governor's orders, McGarrett and Grover join forces to bring in a skilled computer hacker. Nick Jonas guest stars. (S4, ep 8)
McGarrett juggles a deadly plot to kill the US president with a visit from his aunt (guest star Carol Burnett). (S4, ep 9)
After the attempted murder of a Pearl Harbor veteran at a remembrance ceremony, the team investigate a decades-old crime. (S4, ep 10)
Danger looms when the discovery of a dead body leads Chin onto the trail of a serial killer. Contains violent and distressing scenes. (S4, ep 11)
McGarrett tries to track down the Captain's friend, who is wanted for murder, while Kono continues her search for Adam. (S4, ep 12)
Emotional wounds are reopened when Chin finds out the identity of his father's killer. Contains violent and distressing scenes. (S4, ep 13)
Tensions mount when McGarrett and Danny are kidnapped by a convict desperate to clear his name. Michael Madsen guests. (S4, ep 14)
A surprise is in store for Danny when his mum (guest star Melanie Griffith) stops by. Contains violent and distressing scenes. (S4, ep 15)
Conspiracy theorist Jerry Ortega (returning guest star Jorge Garcia) helps the Five-0 solve a triple homicide. (S4, ep 16)
Danny forces a reunion between his parents, while Jerry helps McGarrett decipher a code at the bottom of his champ box. (S4, ep 17)
Chin Ho's high school reunion is interrupted by the grisly murder of a tycoon in an extra special episode voted for by viewers in the US. (S4, ep 18)
Concerns grow for McGarrett and Danny when a bad tip-off leads the team to an abandoned building rigged to explode. (S4, ep 19)
The murder of a swimming pool cleaner leads the Five-0 to a cell of radicalised students plotting an attack on US soil. (S4, ep 20)
Catherine receives a dramatic blast from the past, prompting her to make a life-changing decision. (S4, ep 21)
O ka Pili'Ohana ka 'Oi (Family Comes First): Desperate times call for desperate measures in this gripping season finale when Grover's daughter is kidnapped. (S4, ep 22)