After Scotty is granted therapeutic leave after a head injury, Kirk and Bones take him to Argelius II to visit a nightclub that has a sort of gypsy/Arabian Nights theme going on. Scotty seems to be recovering nicely and chats up a dancing girl named Kara. Kirk and Bones decide to leave Scotty alone with his new friend, but stop when they hear a screech from an alley. Kara is dead and Scotty is standing over her as if in a trance.
An inquest is held. Administer Hengist calls for Scotty's immediate arrest. Scotty can't remember a thing. Jaris introduces them to his empathic wife, Sybo, who will use her psychic powers to deduce who the killer is. Kirk wants to do things by Argelian law, but he certainly doesn't want to lose Scotty, yet, this "psychic" seems like just another superstition.
When Yeoman Tarkis turns up dead and Scotty unconscious nearby, things look bad.
The crew finally agrees to a seance. Sybo goes into her trance and states she senses a great feeling of anger and hatred towards women and a desire to feed on fear. She mentions the name "Redjac" and states that he has a hunger that will never die. But Sybo will. When the lights come back on, Sybo has a knife in her back and Scotty has blood on his hands. Oh Crap
Scotty, Jaris, Hengist and two other persons of interest (Kara's father and her ex-boyfriend) are beamed aboard the Enterprise
with Kirk and Bones. Scotty is further questioned, using the ship's computer as a lie detector. The conclusion is that Scotty does not know if he committed the murders. He remembers black outs, coldness and a stench like a slaughterhouse. Kirk suggests using a brain scanner to learn what exactly happened. Then, Hengist suddenly goes berserk....
Tropes for this episode include:
- Belly Dancer: The first thing we see in the episode is Kara performing at the nightclub with finger cymbals.
- Bloodless Carnage: Kara is stabbed "dozens of times", Yeoman Tankris is stabbed "over and over again", yet neither bodies bear any wounds and there's no blood at all until Sybo falls over with a blade in her back.
- Clear My Name: Kirk's initial goal is to absolve Scotty of murders that he just knows he couldn't commit.
- A Day in the Limelight: Probably Scotty's most developed part in the entire series.
- Emotion Eater: Redjac feeds on fear
- Everybody Laughs Ending: Justified. Redjac feeds on fear, so Bones injected everyone with mood lightening drugs that made everyone super cheerful. Kirk observes that for the next few hours, he's going to have the happiest ship in the fleet.
- Fair Play Whodunnit: Well, Knox's 2nd Commandment (no supernatural or preternatural agencies) is blown to Hell. Number 7 (the detective could not have committed the crime) could be considered broken, depending on if you would see an administer as a detective.
- Hey, It's That Voice!: Piglet is on a killing spree!
- He-Man Woman Hater: Redjac. Scotty was said to be temporarily distrustful of women because a woman caused his accident. He seems over it by the time he meets Kara.
- Historical Rap Sheet: Redjac is a noncorporeal lifeform which has been a serial killer on several planets, including Earth where it was Jack the Ripper as well as a few other unnamed killers (in China in 1952 and Kiev in 1974).
- Jack the Ripper: Redjac's original incarnation. Incidentally, while the unidentified murderer was known as "Old Leather Apron" and "Saucy Jack", he was not known as "Red Jack".
- Laser-Guided Amnesia: Scotty just can't seem to remember what happened when he was alone with those women.
- Lie Detector: The ship's computer can act as one. We must assume it is more accurate than modern polygraphs.
- Lights Off, Somebody Dies: How Sybo is killed
- Mouthful of Pi: Spock prevents Redjac from taking over the ship's life support systems by ordering it to calculate the last digit of pi.
- Ominous Fog: Odd juxtaposition. Scotty describes the fog of Aberdeen to be almost romantic. (He feels that way about anything Scottish.) Kirk and Bones leave the club to be surrounded by a thick fog not dissimilar from what would be found in a film on Jack the Ripper.
- People Puppets: How Redjac commits his murders, being a Puppeteer Parasite. Maybe Dead Person Puppet in Hengist's case.
- Spooky Seance: Sybo hosts one. It's her last.
- Values Dissonance: Redjac feeds on fear, and Spock says that it's targeted women because they're more easily terrified.