Catacomb — An Edinburgh Adventure Horror Novel

The story

A monster beneath Edinburgh, a thousand-year bargain, and a father with one night to bring his daughter out.

Walker Kane didn't believe in monsters. Until they took his daughter.

Beneath the festival streets of Edinburgh, an ancient evil waits. Each year the Grendsluagh demands a human sacrifice in exchange for the city's prosperity, and a secret society known only as the Cabal has kept the bargain for centuries.

When ex-military search and rescue officer Walker Kane's estranged daughter Emily is taken, all he has is the locket she dropped as they carried her away, and one night to reach her.

Aided by a mythology-obsessed librarian and a daredevil urban explorer with her own debt to the darkness, Walker descends into a labyrinth of bone and fire, where saving Emily will cost him everything.

“As the prick of a needle pierced her neck and she sank into blackness, Emily's last thought was of her father. Find me, Dad. Please.”From Catacomb · chapter 5

Taken meets Beowulf beneath the streets of Edinburgh.

Read it

Buy Direct Amazon Other stores

Available in ebook, paperback, foiled hardback, large print and audiobook. Buying direct supports the author most, and ships worldwide.

Reader reviews

“Heroic librarian character? Yes please! ... I ended up reading it in one sitting because I had to know what was going to happen next ... a thrilling way to spend an evening!”Stephanie C., reader review

“Gripped me from the first word and carried on until the last page. Your imagination will take over completely and you are with Walker, Laurel and Max from start to finish. A real page turner.”Eve, reader review

“Eerie, creepy and set in an amazing location with just enough details to start to wonder if it could be true….myths and legends have to come from somewhere.”Steph, Goodreads review

The research behind the fiction

Catacomb is the world beneath Edinburgh: a labyrinth carved into the extinct volcano under the castle, inspired by the city's real underground vaults. Above, the festival fills the streets with fire and music. Below, a secret Cabal keeps a thousand-year bargain with the Grendsluagh, a monster built from Grendel and the Sluagh of Celtic myth.

Hidden places

The vaults beneath Edinburgh

The real underground chambers and night tours that seeded the book. 'I knew one day I would set a story there.'

Learn more →

Mythology

Building the Grendsluagh

Grendel from Beowulf, the Sluagh from Celtic myth: how a new monster is made from two old ones.

Landscape

Edinburgh's volcano

Castle Rock and Arthur's Seat are the roots of an extinct volcano, last erupted 350 million years ago.

Subculture

Urbex: place-hacking the city

The real urban exploration movement behind Max, from Ninjalicious to Bradley Garrett's Explore Everything.

Origins

Beowulf's monster

Why Grendel still works after a thousand years, and the epigraph that opens the novel.

Theme

The city that feeds

From Omelas to festival cities: who pays for prosperity, and what a place agrees not to see.

Questions

Before you begin

Is Catacomb a standalone?

Yes. It is a complete story in one short novel with a decisive ending and no cliffhanger.

How dark is it?

Dark adventure rather than bleak horror: monster violence comes in fast, visceral bursts, and the ending is cathartic and hopeful. There is no torture and no sexual violence on the page.

What formats can I read it in?

Ebook (Kindle and Kindle Unlimited), paperback, a special foiled hardback with sprayed edges, large print, and an audiobook narrated in Jo's own voice, digitally created.

Is it connected to J.F. Penn's other books?

No shared characters, but the same DNA: an ancient relic, a secret society, and a real city's underworld. Readers of Blood Vintage and the ARKANE thrillers will feel at home, and if you like monster books and the deep ocean, try Bones of the Deep.

Screen rights

Catacomb — adventure horror feature

For a thousand years, a secret cabal of Edinburgh's elite has bought the city's prosperity by feeding one young person a year to the monster in the catacomb beneath the castle. This year they chose the wrong girl: her father is Walker Kane, ex-military search and rescue, and he is coming down to get her.

FormatAdventure horror feature

ToneTaken · The Descent · Beowulf

RightsUnder a shopping agreement (2026)

Rights enquiry Full screen slate →