|Kupu'eu (Fallen Hero)|
|Season 4, Episode 5|
|Air date||October 25, 2013|
|Written by||Moira Kirland & Eric Guggenheim|
|Directed by||Jeffrey Hunt|
A ia la aku
A routine surveillance job for Catherine and Billy ends in tragedy and sets the H50 team on a search for the killer while in Hong Kong, Adam considers making the ultimate sacrifice to save Kono.
On a routine assignment, Catherine and Billy witness a hit man killing their subject, John Cutler, and wounds the two, with Billy later dying in hospital from injuries sustained in the gunfight while Catherine survives albeit with an injured left arm.
Five-0 return to the house to find it had been cleaned out of any evidence.
After finding Cutler's body in his second car, the team learns from his encrypted laptop that he was spying on his wife's security company, on orders from a rival company.
Five-0 realizes that the company's CEO was responsible for cleaning up the scene, but still agrees to give them all the evidence they gathered although the evidence is later discovered to have been contaminated, further complicating the investigation.
Five-0 discover that Billy wounded the hit man, Jason Kroll.
They find him, but he dies before he can reveal who hired him. Catherine finds he was hired by someone at the office of Abbie Maxwell, the mistress Cutler had an affair with. Her receptionist admits he ordered the killing due to his love for her.
Meanwhile, McGarrett asks Joe White (Terry O'Quinn) to track down Doris, only to learn that his mother is active with the CIA again.
In Hong Kong, Adam allows himself to be captured for Kono's safety. The team later say goodbye to Billy who is buried with full military honors.
- Morgue Attendant: Boss said you wanted to see me?
- Joe White: This man's name is William Harrington.
- (He looks down at Billy's face)
- Joe White: Former Lieutenant Commander, SEAL Team 7. He saw action in Iraq and Afghanistan. Served his country with courage and distinction.
- Morgue Attendant: I'll take good care of him, sir.
- Joe White: I'm sure you will.
- (He respectfully pulls the sheet over Billy's head and places his hand on his chest)
- Joe White: I just wanted you to know who he is.
- Masi Oka is credited, but do not appear.
|Alex O'Loughlin||A Navy SEAL and leader of the Hawaii Five-0 Task Force.|
|Scott Caan||2nd-in-command of the Hawaii Five-0 Task Force and Steve's partner.|
Chin Ho Kelly
|Daniel Dae Kim||A member of the Hawaii Five-0 Task Force.|
|Grace Park||Youngest member of the Hawaii Five-0 Task Force, and cousin of Chin.|
|Dr. Max Bergman||Masi Oka||Chief Medical Examiner for the Hawaii Five-0 team.|
|Catherine Rollins||Michelle Borth||An Ex-Navy Lieutenant and Steve's on-off girlfriend.|
|Adam Noshimuri||Ian Anthony Dale||Kono Kalakaua's boyfriend and former head of the Yakuza.|
|Billy Harrington||Justin Bruening||A former Navy SEAL and Catherine Rollins's ex-boyfriend.|
|Joe White||Terry O'Quinn||Former Navy SEAL CO, and Steve McGarrett's mentor.|
|Sgt. Duke Lukela||Dennis Chun||Sergeant with the Honolulu Police Department.|
|Abbey Maxwell||Lacey Beeman||A woman who appeared in the previous episode.|
|Sandra Cutler||Monica Lacy||A woman who appeared in the previous episode.|
|Lee Benner||Larry Poindexter|
|Andrew Burns||Logan Fahey|
|Tom Harrington||Thomas Allen|
|John Cutler||Paul Bauer|
|Jason Kroll||John Mark Harmon|