It's Halloween in O'ahu, and Five-0 must track down a serial killer inspired by Frankenstein. Also, Jerry calls Five-0 for help when an armed gang raids a blood bank, and Danny must track down Grace who lied and snuck out to a Halloween party.
While Five-0 works the case of a murdered bounty hunter who apprehended a dangerous killer, Danny's ex-wife reveals a shocking secret to him that will change his life forever.
In order to stop a meth epidemic on the Island, McGarrett and Danny go undercover as pilots, but when McGarrett is seriously wounded, Danny is forced to break their cover in order to save his partner's life.
As Max prepares to say goodbye to his Five-0 ohana, they must investigate a murder during a police convention on the Island. Jimmy Buffett returns as Frank Bama.
When a man is found left for dead drifting off the coast of Oahu, Five-0 uncovers a deadly slave trade operating aboard an illegal fishing vessel. Also, while Danny is out with his children, his car is stolen so he commandeers a bus to chase down the thieves.
