The Doctor and Leela arrive in England and immediately run across the slime trail of the titular White Worm. The Worm is a local legend that originated in Roman times. The creature supposedly kidnaps and consumes the unlucky. The Doctor and Leela are separated, and while the Doctor spends some time with the mysterious Demesne Furze, Leela encounters the eccentric Colonel Spindleton and his mysterious servant in the basement...
The story ends on a cliffhanger that leads into The Oseidon Adventure, the final story of Big Finish's first series of Fourth Doctor Adventures.
- Backhanded Compliment: When Leela makes a joke, the Doctor says "That's nearly very good."
- Badass Boast: The Doctor on Leela's behalf, saying that Leela versus a Chieftain tank is not a fair fight, and they should probably do something about it while the tank's still in one piece.
- Egomaniac Hunter: Spindleton, who went a bit insane on his return from Africa. Not averse to Hunting the Most Dangerous Game.
- Getting Crap Past the Radar: When the Worm explains it was worshiped as a "symbol", Leela asks what it was a symbol of. She doesn't get an answer.
- Literal-Minded: Leela, as usual. The second time someone has to explain to her that they were using a figure of speech, she comments "The Doctor is always using those. It can be very tiresome."
- Private Military Contractors: Some chaps who helped Spindleton out in Africa, and have a helicopter.
- Scaled Up: Inverted, the Worm is Mrs Furze's natural form.
- The Scottish Trope: The huntsmen refer to the Worm as the "You-Know-What". When the Doctor calls it a serpent John tries to correct him, but Carswell interrupts him before says what it is. The Doctor gets into the act by saying there's also a "Something or Other".
- The '70s: The story is set in the 1970s, with numerous pop culture references from that time.
- Shout-Out: Tarzan is referenced by the Doctor once. Leela uses the Doctor's scarf to swing over an electric fence and gives the classic "Tarzan yell" while doing so.
- Swallowed Whole: Leela and the Doctor
- Tank Goodness: Colonel Spindleton is very fond of his remote-controlled tank.
- You Do NOT Want to Know: Combined with The Scottish Trope to provide far too many "you knows" in one exchange:Carswell: You know what they say that that ... You-Know-What can do.Doctor: What is it they say the You-Know-What can do?Carswell: You don't want to know.