As much as “Hawaii Five-O” fills the heads of faithful fans with dreams of days on sunny beaches, they eagerly look forward to trading summer days for the start of fall, when their favorite crime-fighters return for another season. On September 28’s premiere episode for Season 9, “Ka ‘owili oka’I” (Cocoon), Steve McGarrett (Alex O'Loughlin) finds himself on a ship again, but not the same one where he left off on Season 8. [VIDEO] This time, the Lt. Commander who answers to “only the governor and God,” according to a familiar female flame who enters this picture, is after a traitor agent on the inside, whose information is costing the lives of CIA agents.

One of those agents is Tom Hennessy, an old friend of Steve’s, who helped track Victor Hess, the killer of Steve's father.

Steve never forgets a friend or a faithful helper in law enforcement, and he has the support of his full “Hawaii Five-O” force as he becomes a subject of sensory deprivation in order to spread tracking-approved malware onto a spy ship’s system and identify the mole. The commander’s experience recalls visions of his greatest nemesis, Wo Fat, portrayed by Mark Dacascos, and a reality he doesn't want to face.

From burying cash to losing a brother

The story opens with Junior (Beulah Koale) helping Steve with digging a clandestine hiding spot in Steve’s backyard for a load of cash from Kamekona for the restaurant venture with Danny (Scott Caan). Kamekona does a lot of good through his “strictly cash” transactions, and Steve wants to honor his generosity while still keeping assets “liquid,” especially because Danny is better at bringing in the family than balancing the books.

Steve defends that he doesn't want to get into legal papers and lawyers, and dismisses Tani’s (Meaghan Rath) cautions about doing business with family, no matter how “ohana.”

In a lovely nod to "Hawaii Five-O" history, the opening credits are in the original's style.

The call comes that Hennessy's body has been found, and Steve understandably takes this crime scene very personally. By the time they arrive at the agent’s apartment, valuable pages from a diary have already been burned by Kang (Roger Yuan), a counter agent sent to take care of the scene. Danny and Steve almost have more than they can handle to take care of this opposition, but a crowbar finally gives Steve the upper hand, despite causing a spat with Danny because their suspect is deceased and impossible to question.

While they are at the scene, a familiar agent to Steve, Greer (Rochelle Aytes) arrives with Miller (Jack Coleman). Danny instantly notices that familiarity, but Miller dismisses Danny, to which Steve retorts, “He's Detective Danny Williams to you,” and refuses to “stand down on a homicide,” which he's out to prove.

Danny sees a romantic potential for his partner, and he pleads that Steve needs to “stop living like a monk,” and perhaps he and Greer can share “grown folks business” after the case is solved. Steve refutes any part of that, playfully locking Danny out of the car. He does, however, call Greer to meet him, and she plants the seed of someone from the inside being responsible for five agents in five locations being killed.

Deception in deep water

The only actual words on the burned bits of paper retrieved from the scene are “cocoon” and “Arcturus,” which Steve later reveals as “SS Arcturus,” a spy ship. Noelani (Kimee Balmilero) also discovers a sealant substance in the eyes, ears, and nose of Tom Hennessy's body.

Steve and Danny scout the SS Arcturus, and “older Steve” determines that he will come on board without using his extreme Navy Seal maneuvers this time. He hides on the welding crew of the ship and discovers a holding area with a sensory deprivation tank and scientists in lab coats.

With full backup from “Hawaii Five-O” at strategic points, Steve goes in for the infiltration. As he nears the tank area, he is injected with medication, rendering him helpless. He does recognize Greer as one of his assailants. As he is being placed in his fully submergible suit, he is warned that he will break after a number of hours and that his mind will go blank, and he will reveal secrets.

His observers start to see signs of aa hallucination after six hours, as Steve sees visions of Wo Fat from the past as his tormentor in a lab coat. They pull him out from the pool and cut through his head coverings. From the outside, the team observes Greer making a getaway and making “Hawaii Five-O.” She alerts the crew of the ship to get men outside.

The ever high-adrenaline shoot-out scene progresses, and Junior and Tani enter the ship from a downed communication tower. Steve somehow musters the physical strength he couldn't seem to find in that apartment, even after more than six hours underwater. He even does incredible things with a metal procedure tray to take care of one malicious offender. Just call him the hero in the red rubber suit. When he is underwater again, dragged by his scientific torturer, Danny pulls him to safety.

The devotion in this long-running “bromance” is displayed fully intact, as Danny asks, “Who am I?” of his dripping partner. “Danny Williams,” responds Steve after some squinting. “How long have you known me?” Danny further questions. “Fifty years,” McGarrett answers. The credits roll just after "That’s not funny,” and “Thank you,” are exchanged between the two, and another season sets sail.