After an introduction by an omniscient narrator, the Celestial Omnibus comes out of The Maelstrom, arriving at a stormy cathedral in the middle of the night. A verger comes out in the downpour, claiming that the cathedral is haunted. Iris and Panda welcome the verger aboard the bus, so he can spend the night there.
In the morning, Iris, Panda, and the verger talk over breakfast, learning about each other and the cathedral. The verger decides to give Iris and Panda a tour of the cathedral, to which Iris and Panda agree. On the tour, Iris and Panda note how ugly and mismatched the cathedral is. The cathedral's bishop tells Iris, Panda, and the verger that certain parts of the cathedral are closed, due to them being fuly booked. He tells them that he is holding a meeting with the Soroptimists. He then dramatically leaves.
With no other place to really go, the verger leads Iris and Panda to the gift shop, where they group reads a book about the hauntings of the cathedral. After reading about the questionable stories, they hear a scream from the bishop, which they go off to investigate.
When they reach the room where the bishop is giving his presentation, they see that a spectre is ghoulishly menacing at the the bishop and the Soroptimists. The ghoul then dissipates. Iris then finds the room is full of static electricity, and she figures out that all of the hauntings in the book that the verger had read were in fact the same haunting, but the pattern is only getting stronger as time goes on.
Hours later, the trio head down into the cathedral's crypt, where they find a tomb. The verger opens the tomb, which is in fact part of a buried spaceship, to find a humanoid corpse covered in a dried, blood-like substance. Iris tastes it, and she determines that it's not blood, but some sort of iron crust. A creature appears behind them, not unlike the one that taunted the bishop. It tells them to stop interfering, which Iris completely ignores. It scampers, leaving some fabric behind, which Iris knows shouldn't exist until twenty years in the future. Iris deduces that it's not a conventional type of haunting - instead of a paranormal entity haunting the present from the past, it's the present bring haunted by the future. Iris knows trying to fight it would be futile, so she and a reluctant Panda return to the Omnibus. However, the Omnibus refuses to start.
The verger has an idea on how to stop the hauntings - to change the future so they hauntings can't exist. The trio try everything they can to discredit the hauntings, however it's entirely futile. So as a plan b, Iris builds a time bomb out of bits from the Omnibus, so she can attempt to explode the buried ship.
At midnight, Iris and Panda head down into the crypt with the bomb, and the closer they get to the tomb, the slower time gets. Iris then chucks the bomb, but it stops in mid air as time halts to a standstill. Due to the strain, the bomb then breaks apart. Iris devises a new plan, literally out of thin air. Iris devises that in order to defeat the spectres from the future, she and Panda must in fact become the cause of all of the paranormal activity over the history of the cathedral. Despite Panda being perplexed by Iris' plan, Iris is adamant that it'll work. The bishop arrives, revealing that everything he did was how a not-too-distant future Iris had instructed him to do, including stealing the spark plugs from the Omnibus.
Finally, the narrator returns to say that Iris and Panda were successful in their plan. The narrator shows us a conversation that Iris and Panda are having, and Iris tells Panda that she can sometimes see outside the narrative - and she gives us, the reader, a fourth-wall breaking wink.
- Iris listened to an album by Neil Sedaka.
- Iris whistled a Dusty Springfield song.
- The cathedral is a palimpsest.
- Iris helped out in the excavation of Stonehenge.
- Panda mentions the Jolly Green Giant, William of Ockham, and Winifred Atwell.
- Iris and Panda had previously met Dan Farson.
- The bishop used a PowerPoint presentation.
- The verger mentions that the bishop was on Radio 4, and that the experience had boosted the bishop's ego.
- The gift shop stocked copies of "Ghastly Ghoulies", "The Crypt Key Curse", "The Dwarf in the Mask and other Town Tales", "More Recipes from a Monastic Garden", and "The Bumper Book of Local Haunts".
- The bishop served Battenberg cake at his presentation.
- The bishop recalls that he refused to let Yvette Fielding into the cathedral.
- Iris mentions the Very Fabric.
- Iris watches an episode of Scooby-Doo.
- The creature that appeared in the tomb had a voice not unlike Orson Welles.
- Rabbit Chat & Date was a mobile app that the verger had installed on his phone.
- Iris refers to herself as a flâneuse.
- The creature's rags are made out of Lycra.
- Panda drinks multiple Malibus.
- Iris uses a Give-a-Show Projector to orchestrate the ghosts.
- The Celestial Omnibus uses spark plugs.
- The names of the verger and the bishop are are left deliberately ambiguous. Panda even observes that he couldn't remember the name of the verger.
- It's entirely possible that in this story, that the hauntings by the ghosts never actually existed, but were just a result of a Bootstrap paradox.