The Plot
"I Demand an Explanation"

I'm smiling as I type this.

To be perfectly frank, if you don't already know what goes on in this movie, this probably isn't the project for you. But who am I to question a time-honored format. Fans, if you know the movie and you wanna just skip to the next chapter, feel free.

The obligatory plot summary follows.

Three parapsychologists—Dr. Peter Venkman (Bill Murray), Dr. Raymond Stantz (Dan Aykroyd) and Dr. Egon Spengler (Harold Ramis)—are summoned to the New York Public Library to investigate a haunting. After an admittedly unsuccessful encounter with their first actual ghost, they return to their university in high spirits, only to find their grant terminated and their eviction underway. Undeterred, Venkman sees potential in their progress, and convinces his colleagues to take their research to the private sector: "Professional paranormal investigations and eliminations."

They set up shop as 'Ghostbusters'—essentially, ghost exterminators—converting an old firehouse into their headquarters and constructing all manner of hazardous nuclear equipment. But business is slow to start, and their secretary, Janine Melnitz (Annie Potts), has little to do.

Around this time, symphonic cellist Dana Barrett (Sigourney Weaver) has a paranormal encounter in her Upper West Side apartment. It leads her to a spectral vision within her refrigerator, starring a terror dog howling the moniker 'Zuul'. She takes her case to the Ghostbusters, whereupon Venkman promptly falls in love with her. He confesses his feelings as he investigates her apartment, without success on either front.

That night, the Ghostbusters get a call from their second client—the ritzy Sedgewick Hotel, caught in the throes of a recurring disturbance. The target is a pesky green ghost (Slimer, as himself). After some false starts and destruction of property, our heroes figure out how to stun and capture the ghost and encase him in a trap; after collecting their fee, they bring him home to a specialized storage facility in the firehouse basement.

The victory at the hotel is only the beginning; an unprecedented wave of supernatural activity has New York reeling, and the Ghostbusters find themselves busier than ever, leading them to take on a new man, Winston Zeddemore (Ernie Hudson). Venkman, meanwhile, is making progress on both Dana's case and her affections: he meets her at Lincoln Center to inform her that Zuul was a demigod subservient to the Sumerian deity Gozer, then asks her out for Thursday night. The date is made.

Venkman returns to the firehouse to meet Walter Peck (William Atherton), representing the Environmental Protection Agency. Peck expresses concern over the potential environmental impact of the Ghostbusters' activities, particularly with respect to the storage facility. He asks to inspect the premises; Venkman refuses. There's a brief clash of personalities, and Peck threatens to return with a court order.

Peck's visit couldn't have come at a worse time. The storage facility is beginning to overflow, psychokinetic turbulence in New York is mounting, and Spengler, employing an unforgettable Twinkie metaphor, foresees "something big on the horizon."

Thursday night, something big indeed begins to brew. Dana and her nerdy neighbor Louis Tully (Rick Moranis) are attacked by terror dogs, agents of Gozer. Venkman arrives for his date only to find Dana possessed, introducing herself as Zuul, the Gatekeeper; Louis, eventually turned over to the Ghostbusters' custody, proclaims himself Vinz Clortho, Keymaster of Gozer. Both the Keymaster and Gatekeeper speak in apocalyptic prophecies, dovetailing uncomfortably with a conversation Stantz and Zeddemore have about the Biblical tales of Judgment Day.

Venkman sedates Dana/Zuul and heads home on Friday, just in time to meet Peck, who has returned with a sheaf of legal papers, a Con Edison man and a heavy grudge. Despite Spengler's protests and Venkman's belated attempts to cooperate, Peck orders the protection grid on the storage facility shut down. This act causes an explosion and frees all the ghosts, with the resultant psychic disturbance awakening Dana. The Ghostbusters are arrested. Louis sneaks off in the chaos, seeking Dana as ghosts wreak havoc all over the city.

The Ghostbusters confer in jail. Stantz and Spengler have determined that Dana's apartment building is a "superconductive antenna" for psychokinetic energy, designed by cult leader Ivo Shandor as a gateway to the spirit world, and a place for Gozer worship: "Bizarre rituals intended to bring about the end of the world, and now it looks like it may actually happen."

Overwhelmed by the spectral crisis, the Mayor summons the Ghostbusters from the lock-up. Also on hand are various city officials, the archbishop, and Peck. In the end, the city puts its trust in the Ghostbusters. A joint effort between the police and the National Guard is coordinated to escort the Ghostbusters to Dana's building, where the coming of Gozer is at hand.

Our heroes arrive at the temple atop the apartment building just in time to witness the final step in the Keymaster-Gatekeeper ritual, and the emergence of Gozer. A brief skirmish ensues, and the form of Gozer vanishes, leaving behind only her disembodied voice: "Choose the form of the Destructor!" Realizing that they are being asked to summon something designed to kill them, Venkman commands the group to clear their minds and think of nothing, but it's too late: Stantz' imagination turns to a beloved advertising icon from his childhood, the Stay-Puft Marshmallow Man, and in short order a jolly marshmallow behemoth is stomping up Central Park West.

With death nearly upon them, Spengler seizes upon a last-ditch idea; they might close the gates to the spirit world by crossing their proton streams, a scenario previously agreed upon as a life- or even world-ending blunder to be avoided. With no other choice, Venkman leads the assault. They fire into the open gates; all four streams are crossed, generating a massive overload of energy in the spirit world, shutting the doors, destroying both the temple and the marshmallow man.

The Ghostbusters regroup. For a moment, they fear Dana dead, encased in a ruined terror dog husk; but her hand breaks through, and they extract her from the ruins. Louis is all right as well, and they all exit, stage left, with the last line going to a jubilant Zeddemore: "I love this town!"

A grateful crowd gives the Ghostbusters a heroes' welcome back on the ground, and Venkman and Dana share their first kiss. The Ghostbusters ride off with Dana in tow, leaving Slimer to end the film, careening toward camera just before we fade out.