If it's the Halloween episode, Jerry must be in the middle of it.

Sure enough, Jerry tried to find proof of a murder that had haunted him for decades on Hawaii Five-0 Season 9 Episode 5.

The best part was that he even had his own Scooby Gang to help him solve the mystery.

No Mystery Machine, though. Bummer.

Of course, Jerry thought he saw an ax murder while he was at Camp Hina in 1982. In the dark by himself.

Jerry was a heckuva storyteller even then, so much so that his cabin mates didn't believe him.

Related: Hawaii Five-0 Season 9 Episode 4 Review: The Long Ride Home

They don't believe him now, either. But they've established a Halloween tradition of returning to the scene of the crime every year. There were Crystal and Ano, who came to support Jerry as he searches for his white whale.

Maybe that's a bad analogy, as Jerry has so many white whales.

Anyway, Eric came along to lend a hand. It's good to see that Eric is still around.

Eric even persuaded Noelani, who made a very believable Velma, to help out. It was good to see the medical examiner Halloween tradition has been passed on to her. I really miss Max's Keanu Reeves costumes.

I like fun, sarcastic Noelani, and wish we got more of her. She's actually gotten better play on Magnum PI lately.

I missed Jerry having a highly creative costume this year, although Gravedigger Jerry was an interesting look.

Related: Watch Hawaii Five-0 Online: Season 9 Episode 4

I guess instead we got Young Jerry, an inspired bit of casting, as Jerry took everyone through his experiences on that fateful night, so long ago, when he escaped the Ax Man, who he had determined was Bo Bradley, who lived adjacent to the camp.

Through the years, Jerry had even determined whose body it was, a missing teen girl. Now the camp's been sold to a developer, and this was his last chance to prove there had been a murder, 

It was enjoyable to see the episode mine most horror cliches, including a creepy old guy in the woods and kids trapped in a cabin by the killer.

Then those cliches got turned on their head, as Bo Bradley, the creepy old guy, shot the Ax Man and saved the kids. Then he and Jerry got to bond over hot cocoa, as Bo admitted he knew about Jerry's stories, which helped keep campers off his land.

And jinkies! Just like on Scooby Doo, the monster was an obscure character from Jerry's past, his camp counselor. Ruh-roh! It was vindication for Jerry, even if he got one crucial detail wrong -- the actual killer. Good thing he's not, like, a detective or something.

The other case had a Poltergeist feel to it, with a mysterious blonde girl popping up at the heart of it.

Related: 45 Baddies We Unapologetically Adore

It had an admittedly spooky feel to it when a mother recognized a murder scene from her daughter's drawing. Only it wasn't her drawing, but rather a drawing from her imaginary friend, Molly.

Only Molly was real, with her image jumping off the parents' monitor. My first thought was the little blonde girl from Poltergeist saying, "They're back."

Tani broke open the case by suggesting that the dead woman's necklace get swabbed for DNA. I thought McGarrett was taking a real leap when he suggested that Molly had drawn three separate crime scenes and they had a serial killer on their hands, but damned if he wasn't right.

A father dragging his daughter along to witness his crimes was Criminal Minds-level icky, but at least they wrapped up the case in a whole lot less time. I just hope Molly's clean mother can get her the help she'll definitely need.

And, from the "be careful what you wish for" department, Captain Keo got back to Tani, and (surprise!, surprise!) the gun she found at Adam's house was the one used to kill Noriko. Otherwise, you've got no storyline.

Related: Get CBS All Access via Amazon Channels for Hit Shows, Exclusive Originals & Live TV

How does Adam explain that gun in his house? Either A, "That gun was planted here," or B, "I'll holding that for X." I can't imagine it will linger over him for any length of time.

Adam is supposed to return for the 200th episode Nov. 9, with the restaurant also opening the night, in what promises to be a cameo-fest. Wouldn't it be cool if they could get Old Rick and New Rick from the two Magnums to show up for the same festivities? That's probably too much to hope for.

But at least two long storylines will reach their overdue conclusions. 

To recap those storylines, watch Hawaii Five-0 online.

Which story was spookier -- Jerry's or Molly's? How'd you like Noelani's costume? Was this a very special holiday episode?

Comment below.

Dale McGarrigle is a staff writer for TV Fanatic. Follow him on X.