In the evening, when everyone's in bed except Egon, who is still working, there is an earthquake. Meanwhile, a police car flips over and the officers get out and notice a light shining from a subway. They take photos, as a red orb flies out. The senior officer tells the other to take the film to the station while he guards the car, then the red orb turns into a fire-breathing monster, then into a well-dressed man.
The next morning, the Ghostbusters clean up the mess, and Egon notes a surge in psychic activity. The police arrive and show the Ghostbusters the photos, and Peter assures them they can catch it. Egon is irate at this assumption, but Peter thinks all they need to do is look it up.
At the pier, two ships crash, but a worker on one of them turns into the red creature, who flies the ship into the docks so it won't sink. Meanwhile, Egon looks the entity up on his computer and finds that his name is Marduk, and he's a benevolent Babylonian god, but has a nemesis named Tiamat, a five-headed dragon.
At Central Park, Marduk changes from a random man to a sailor, then hails a taxi. However, a green orb shows up and morphs into Taimat. Meanwhile, Ecto-1 is causing a traffic jam due to Egon stopping to repair a faulty doohicky on the roof. A burly guy gets angry with them, but backs off when he mistakes the doohicky for a weapon. Once it's fixed, Egon picks up the signal from both entities.
While Tiamat wreaks havoc on Central Park, the Ghostbusters find Marduk at Central Station. They chase after him and he changes form several times. Eventually, they catch up to him when he takes the form of Santa, and he admits to wanting to live in New York. When Tiamat shows up, Marduk wants to defeat him, but the Ghostbusters decide to fight him themselves (with Central Park closed and police keeping watch) since they believe that would be less destructive. Eventually, they disintegrate Tiamat, and believe that Marduk also disintegrated due to an "ecto symbiosis" (when two supernatural entities can't exist without each other), but it turns out, he was just taking the form of a horse.
This episode provides examples of
- Animorphism: One of Marduk's forms is a horse.
- Aside Glance: At the end, Marduk (taking the form of a man) tips his cap to the audience.
- Benevolent Monsters: Marduk's true form might be a large, red monster with horns, but he still wants what's best for humans.
- Did You Just Punch Out Cthulhu?: The Ghostbusters manage to destroy Tiamat, the nemesis of a god.
- Dramatic Irony: The Ghostbusters never find out that Marduk didn't disintegrate.
- Extra Eyes: Marduk has four eyes in his default form.
- Fun T-Shirt: Technically, a sweater vest — one guy wears a sweater vest reading, "I [heart] NY".
- Green and Mean: Tiamat is a green dragon, who's Marduk's arch-nemesis.
- Mythology Gag: Marduk asks the Ghostbusters if they're gods, referring to the movie, where Gozer asks the same question.
- Playing with Fire: Marduk can breathe fire.
- Red Is Violent: Subverted — Marduk's default form is red, and Winston fears he'll be bad, but Egon assures him he's good.
- Sexshifter: Marduk is a male god, but once takes the form of a nun.
- Shock-and-Switch Ending: At first, the episode seems to be ending happily, since Tiamat gets destroyed. However, then, it seems to be headed for a Bittersweet Ending because Marduk seems to also be destroyed. But he's not, so it's a happy ending after all.
- Shout-Out:
- The title references a song by ABBA.
- Peter once makes a joke about Smokey Bear in regards to the fire.
- Voluntary Shapeshifting: Both Marduk and Tiamat can shapeshift.
