Five-0 must go up against an aggressive U.S. marshall, Lincoln, when a man wanted for murder escapes capture and seeks asylum in the sovereign land belonging to the Nation of Hawaii.
McGarrett and Danny spend Valentine's Day with their girlfriends, while the rest of Five-0 investigates the murder of a man who had been taking classes on picking up 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.
When McGarrett gets a tip that someone is plotting a terrorist attack on Oahu, Five-O searches for those behind it before it's too late. Also, Chin and Abby have a very difficult decision to make.
McGarrett puts his life in lethal danger when Five-O puts a risky plan to rescue a group of young girls from a sex trafficking ring in motion, Kono decides to make a life- altering choice because of the unique strain caused by the case.
McGarrett and Five-0 help save an injured police dog and in turn use him to find who killed his partner and ambushed his team making a drug bust. McGarrett receives a visit by a former SEAL, who asks McGarrett for a job on the task force.
Local big shot crime boss Jimmy Okada gets hit in a rather spectacular fashion, and Five-O's old friend from MI5, Harry Langford, lends a hand on the case.
The lives of Five-0's informants are in danger when the HPD system is hacked and one ends up dead, forcing McGarrett to enlist the help of hacker Aaron Wright (Joey Lawrence), who he just imprisoned. Joey Lawrence Returns as Aaron Wright.
McGarrett and Adam join Junior at a bank heist in progress, forcing all of them to make difficult decisions in how to proceed into the bank and after the suspects. Tani has issues with a family member and gets advice from Lou.
When investigating a deserted yacht adrift at sea, McGarrett, Danny, Tani and Junior are exposed to a deadly bioweapon and the rest of Five-0 have only eight hours to find an antidote.
When Danny is shot while quarantined in the hospital with McGarrett, Tani and Junior, he's left unconscious and clinging to life, imagining a future for everyone in Five-0.
Danny, still recovering from his gun shot wound is telling his son Charlie a bed time story who Steve and a group of veterans are hunting down some fake Santas who robbed a money truck.