Halloween comes to a Hawaii with a new bizarre mystery as Max (Masi Oka) witnesses, and is infected by, a doctor behaving like a zombie during a outside screening of The Rocky Horror Picture Show. Although Five-0 doesn’t accept that the man is actually a zombie, the more the delve into the unusual case the more creepy it becomes. The team discovers the doctor was overdosed with a mind-controlling and hallucinatory drug which was used by his puppet masters to force the doctor to remove the head of a corpse of a young woman who died in a routine traffic accident from the morgue before going into a homicidal rage.
Looking into the young woman’s past, Five-0 discovers she vanished for nearly a month more than a year ago without having any explanation for where she was or what she was doing. During the course of the investigation McGarrett (Alex O’Loughlin) and Danny (Scott Caan) also run across a young man (DJ Qualls) whose story is earlier similar to that of the car crash victim whose death may not have been an accident. With Max’s help, who was just exposed to small elements of the drug, McGarrett and Danny are given a new suspect in a radical doctor who relocated to the island around the time of the beginnings of these mysterious abductions who believes he can alter the brain chemistry of those with violent or criminal tendencies.
Hawaii Five-0 doesn’t skimp on Halloween weirdness with the crazy brain doctor, zombies, and mind-controlling drugs. Although the episode doesn’t have any more scenes with Kono (Grace Park) or Adam (Ian Anthony Dale), Catherine (Michelle Borth) does follow McGarrett’s advice to find a new project to help her work through the guilt of Billy’s (Justin Bruening) death by looking into the Yakuza in both Japan and Hawaii and trying to help Kono and Chin Ho (Daniel Dae Kim) find a way to rescue Adam. Using her sources to work even closer with the team, the show may be finally moving closer to having Catherine join Five-0 full-time.
“Kupouli ‘la” also introduces the concept of Danny suffering from claustrophobia (likely to set up themes of an episode later in the season). Although I don’t mind the plot point, I’m pretty sure that going back over the series you would be likely find several episodes that contradict this idea, which makes introducing it so late in the series’ run that much more puzzling. The episode is also notable for the return of Rumer Willis as Max’s girlfriend Sabrina.