In 1684, a monastery gets invaded by bandits. The abbot gives a book called the Codex of Theophilus to a monk, tells him that it must never fall into the hands of "unbelievers" and the seal must never be broken, and sends him away with the Codex.
In the present, the Codex is being sold at an auction, at which Peter and Ray are. Ray wants a book called The Ectoplasmic Gourmet, but they end up buying the Codex instead because the auctioneer mistook Peter sneezing from the dust he blew off it as a bid and they couldn't afford to buy both books. When they get home, Egon is having trouble building a machine, and then they get a call regarding a ghost in a chimney.
Janine goes out on her lunch break, and wants to read but can't find her book so she takes the Codex instead. When she breaks the seal, a storm begins and then the Four Horsemen of the Apocalypse arrive. The Ghostbusters are on their way back (noting that the client just mistook a stuck cat for a ghost) but then it rains live frogs. The Horsemen show up, so the Ghostbusters get out and trap them, but when they leave, they escape.
At the firehouse, Janine gets an unusually high number of calls, and then a priest named Father Yanos comes to visit. He reveals that he's from the Monastery of Theophilus and failed to stop the seal from being broken. He then adds that they can replace the seal, but the new one's in Greece. The Ghostbusters get on a plane and fly on a rough flight to Greece.
The Ghostbusters and Yanos take a train to the village that's closest to the monastery, then board a rope lift, but the Horsemen sabotage it. The Ghostbusters climb a mountain and get the wax, then, after a bit of a struggle, they trap the Horsemen and seal the trap, thus preventing the Apocalypse.
This episode provides examples of
- Accidental Pun: Peter points out the bad choice of words when Yanos refers to the end of the railway as the "end of the line", since the Apocalypse is nigh.
- Blind Mistake: Peter falls onto the trap due to the wax obscuring his vision.
- Comically Missing the Point: When Ray mentions the "seal impression", Peter barks like a seal.
- Did You Just Flip Off Cthulhu?: Peter tells the Horsemen to go "back to the stable" once they're trapped.
- Did You Just Punch Out Cthulhu?: The Ghostbusters manage to lock up the Horsemen of the Apocalypse themselves.
- Horsemen of the Apocalypse: The Horsemen make an appearance here, as noncorporeal, evil men on horseback.
- Hypocritical Humour: Peter berates Yanos and Winston for kissing the ground, only to kiss it himself when the plane's wing falls off.
- Kissing the Ground: When the plane lands, Yanos, then Winston, then Peter kiss the ground — Yanos because it's his home soil, Winston because he was scared during the flight and is glad to be on the ground, and Peter because the wing broke off the plane because he was glad to be safe.
- Let's Split Up, Gang!: When confronting the Horsemen at the department store, Peter and Egon go one way, and Ray and Winston go the other way.
- Monochrome Past: The first scene that takes place centuries ago is in black and white.
- One-Liner: When Peter lands halfway down the mountain, he says, "Halfway? I'll settle for that."
- Questioning Title?: The title ends in a question mark.
- Say My Name: When Peter falls, the other Ghostbusters yell his name.
- Sealed Evil in a Can: The Horsemen were sealed in the Codex with a literal seal.
- Shaped Like Itself: When Egon's "disintegrator" blows up, Winston says, "When it disintegrates, it disintegrates".
- Shout-Out: The title references Apocalypse Now.
- Slapstick:
- At the auction, the auctioneer blows dust in Peter's face, making him cough, sniffle, and eventually sneeze so hard he falls over in his chair.
- Peter later gets the wax on his face, making him fall over.
- Speak in Unison: The rest of the Ghostbusters yell, "Oh no! Peter!" when he falls.
- Unwitting Instigator of Doom: The near-Apocalypse was partially the accidental fault of the auctioneer (for selling the Codex), Peter (for sneezing and thus accidentally bidding), and Janine (for breaking the seal).
- Why Did It Have to Be Snakes?: Winston appears to be scared of flying.
- Wrong Insult Offense: When Ray insultingly calls Peter "Sneezy" for sneezing at the auction, Peter says, "That's Mr. Sneezy to you!".
