At night, the Ghostbusters are attacking a ghost at a bowling alley. They cause a lot of damage, and they're very tired because of the late hour, but they manage to get the job done. When they get back to the firehouse, Slimer has made a huge mess with food. Everyone is in a bad mood, especially Peter, and they argue over whose turn it is to empty the trap, but eventually Egon does.
In the subway, a group of workmen find a door with a talking face on it, that says, "Do not open until Doomsday!". However, they decide to keep working anyway and the door opens, revealing a portal, out of which many ghosts and demons run and cause chaos.
The Ghostbusters are about to go to bed, when they get called to the subway. When they get there, they find ectoplasm everywhere, living graffiti, and a possessed train full of walking skeletons. The Ghostbusters fight off the creatures, then get off at a station.
There, they take a reading and find that the creatures are the result of "poltergeist energy", stemming from ten miles down the line. Winston trips over a stone tablet, upon which is some Sumerian writing. Egon reveals that he can read in Sumerian and translates the inscription. It turns out that once the "doomsday door" is opened, it could lead to the world ending.
They go to the door, enter (despite being pushed back by paranormal wind and the threat of them possibly being trapped in there for the rest of their lives) and shoot into a round orb at the centre of the portal. They then use a "capture mode" setting to pull all the ghosts and demons back into the portal, then fire at the orb again to launch themselves out of the door, which reseals.
Back at the firehouse, Peter is again angry at Slimer for stealing all the food in the fridge. However, Peter does (secretly, since he's embarrassed to do it) give Slimer a pizza before bed.
This episode provides examples of
- Ambiguously Evil: The face on the door that says, "Do not open until Doomsday!". It appears sinister and is on a door that has potential apocalypse material behind it, yet it is warning the humans not to open it.
- Ambiguously Human: It's unknown whether the skeletons are demons or undead humans.
- Animate Inanimate Object: Invoked when the supernatural creatures make trains, graffiti, etc come to life.
- Bait-and-Switch: Ray comments on how scary the haunted subway is... and then says earnestly, "This is great!".
- Black Comedy: The demonic boat skipper tells the rowers that they have an eternity (since they're all demons).
- Cyclops: Some of the demons have one eye or are walking eyeballs.
- Dem Bones: The subway train is full of walking skeletons.
- The End of the World as We Know It: Allowing "Doomsday" to occur would have resulted in humanity being wiped out and Earth becoming a bleak hellscape.
- Evil Laugh: Several of the demons, and the Doomsday door face, can be heard chuckling ominously.
- Evil Sounds Deep: Downplayed for the face on the door, who has a growly, deep voice and is Ambiguously Evil.
- Extra Eyes: Some of the evil creatures have three or more eyes.
- Go-to-Sleep Ending: The episode ends with the Ghostbusters and Slimer going to bed.
- Green and Mean: One of the train monsters is bright green and terrorises the passengers.
- Instantly Proven Wrong: Peter says he's glad he and the others don't have to go through the portal. Then, Ray says that actually, they do.
- Oh, Crap!:
- The workmen look scared and run off once the doomsday door is opened.
- Peter looks nervous once he realises the train is full of skeletons.
- Red Eyes, Take Warning: A few of the demons, plus one of the skeletons, have red eyes.
- Say My Name:
- Peter yells Slimer's name when he's angry at him.
- When the Ghostbusters are being sucked into the portal, Winston yells, "EGON!" and Ray yells, "WINSTON!".
- Screw This, I'm Outta Here: Twice, Peter tries to turn around and leave while entering the portal.
- Sealed Evil in a Can: The demons were originally locked behind a door, and it's opening the door that lets them out and threatens to cause "Doomsday".
- Smelly Feet Gag: Ray likens preventing the apocalypse to washing your socks so your closet doesn't smell of BO.
