In the wee small hours, a man enters the firehouse. As he walks upstairs, the creaking wakes Slimer up, who wakes up the others in fear that it's the Boogieman. They sneak into the kitchen, but it turns out the intruder is Peter's father. He makes them breakfast, then Peter demands to know why Mr. Venkman came, so he reveals a treasure map and claims the treasure is worth two million dollars or so. Ray wants to go, but the rest aren't so keen — there's a "here there be demons" warning, and while the Ghostbusters have dealt with demons and curses before, they still don't want to slog through a jungle. Peter points out that even if they do find the treasure, they'll have to return it to the Mexicans, but Mr. Venkman points out there's a very big reward for finding it.
Eventually, Ray and Slimer decide to go (with Slimer being bribed with food), and Egon gives Ray a device called the Sub Compact Ectoplasmic Tesseract (SCEPTEC) which combines a proton pack and ghost trap, but can only work a few times or else it freezes all its surroundings.
In Mexico, Ray, Slimer, and Mr. Venkman search for a tour guide, but no one is interested, and a man at a burrito stand claims they're too scared. A man named Paco agrees to be the tour guide, and they hike off, eventually entering a temple, that's home to dragon-like creatures called Coatls. They escape them, but Ray and Mr. Venkman fall down a trap door, so Slimer tells Paco to send help.
Back in New York, the other Ghostbusters get a call from Paco, and they fly to Mexico. They meet up with Paco, who leads them through a chamber where Peter accidentally sets off some falling stone heads. They find the trap door, where Slimer is, but so is a Coatl. They try to trap it, but it escapes, yet it also opens the trap door, freeing Ray and Mr. Venkman. Meanwhile, Egon is picking up PKE readings, and Paco's eyes glow red.
Mr. Venkman reveals that the statue is of the Aztec god Quetzalcoatl, and then Peter realises they're standing on the statue. Then, it turns out that it isn't a statue, but rather the real Quetzalcoatl, asleep. He wakes up and the guys try to shoot at him, but he's immune. They run, but then Egon realises that since Quetzalcoatl hibernates, they must freeze him, so he does so by creating a "psychomagnotheric vacuum" via connecting the proton packs to the SCEPTEC.
They freeze Quetzalcoatl, then leave, but it turns out Paco was a coatl in disguise. Then, everyone flies back and Mr. Venkman and Slimer tell the story to some flight attendants to impress them.
This episode provides examples of
- All Myths Are True: Quetzalcoatl turns out to be real.
- Are We There Yet?: Ray asks, "Are we there yet?" in the jungle.
- Badass in Distress: Ray ends up being kidnapped by Paco.
- Breath Weapon: The coatls can breathe fire.
- The Call Knows Where You Live: Ray is the only Ghostbuster who agrees to go on the adventure, but eventually he gets trapped and the others have to go rescue him.
- Chekhov's Gift: At the beginning, Egon gives Ray the SCEPTEC. Towards the end, this device is used to help with the freezing plan.
- Curse: Discussed when the guys wonder if the "here there be demons" warning means the area is cursed.
- Did You Just Flip Off Cthulhu?: Ray yells at the coatls, and then Peter insults Quetzalcoatl himself to his face.
- Did You Just Punch Out Cthulhu?: The guys manage to freeze Quetzalcoatl, who's explicitly described as a god.
- Distressed Dude: Ray and Mr. Venkman end up falling through a trap door.
- Ectoplasm: Played for Laughs when Slimer gets slime on Ray's face.
- Evil All Along: Paco turns out to be a coatl in disguise.
- Fire-Breathing Diner: Slimer breathes fire because of a chilli burrito.
- Food as Bribe: Two examples involving Slimer:
- First, Ray convinces him to go to Mexico by promising him food there.
- Then, Egon convinces him to test the SCEPTEC by offering him pepperoni pizza.
- Glowing Eyes of Doom: A sign Paco is evil is when his eyes glow.
- Foreshadowing: Paco being a Coatl in disguise is foreshadowed by his eyes glowing red.
- Gratuitous Spanish: The Mexicans mainly speak English, but with a few random Spanish words like "amigo".
- Here There Be Dragons: Played with — the map reads, "Here there be demons", but there are demons in the area, so it's literally correct as opposed to being just a vague warning.
- I've Heard of That — What Is It?: Upon being given the SCEPTEC, Ray excitedly calls it 'great', before realising he doesn't know what it is.
- MacGuffin: Mr. Venkman initially sets out to find a treasure that's worth millions of dollars.
- Mass "Oh, Crap!": Everyone on the scene looks scared when the first coatl, then Quetzalcoatl, show up.
- Mythology Gag: Ray calls Slimer a "spud" like he did in the movie.
- No-Sell: Quetzalcoatl is immune to proton packs.
- Oh, Crap!: Peter looks nervous when he accidentally trips the falling heads.
- Only One Finds It Fun: The only one who wants to go on the adventure is Ray.
- Platonic Kissing: Slimer kisses Peter, Egon, and Winston when they show up.
- Playing with Fire: The coatls can breathe fire.
- Red Is Violent: Quetzalcoatl, an evil god, is red.
- Rip Van Winkle: Invoked when the guys freeze Quetzalcoatl to send him back into hibernation.
- Shared Family Quirks: Mr. Venkman is shown flirting with a group of women, which is something Peter would do.
- Silly Simian: A monkey slaps Ray in the face with a tree accidentally.
- Slapstick: Ray gets accidentally slapped in the face with a tree by a monkey.
- Snakes Are Sinister: The coatls resemble snakes.
- Snow Means Cold: Freezing Quetzalcoatl causes it to snow.
- Stock "Yuck!": A "burritos are too spicy" gag features when Slimer eats a burrito but finds it unpalatably spicy.
- Talking in Your Sleep: Played for Laughs — Egon says in his sleep, "It's just an experiment, and besides, your hair will grow back".
- Terms of Endangerment: Peter calls a coatl "pal".
- That's No Moon: Quetzalcoatl is initially mistaken for a statue.
- Things That Go "Bump" in the Night: When Slimer hears the stairs creaking, he thinks the Boogieman has returned.
- Voluntary Shapeshifting: Coatls can shapeshift, as revealed when Paco turns out to be one.
- Weapons That Suck: The SCEPTEC sucks in its victims.
- You Need a Breath Mint: Parodied when Peter tells a coatl that it should do something about its breath, referring to it breathing fire.
