On October 31, children raced through the neighborhood dressed in their costumes. Upstairs in the Firehouse, Peter was getting ready for his date with Lynn Stacy after a gig at a junior high school. Ray revealed everyone else was going trick or treating. Slimer spent the past week making his own costume. Peter found himself face to face with himself, or rather Slimer dressed up as Peter. Peter got an idea and returned dressed as Slimer then slimed Slimer. Meanwhile, downstairs, Lynn arrived and asked Winston if Peter was around. Winston was startled at first but went upstairs. While Lynn waited, Slimer arrived still in costume. Lynn mistook Slimer for the real deal and asked for a kiss hello. Naturally, Slimer went overboard. Disgusted by the act, Lynn stormed out of the Firehouse. Peter was confused and chased after her. However, waiting just outside were two men.
The Ghostbusters were confronted by Dr. Crowley and his assistant Fairweater, who wanted their help in ending Halloween. Crowley insisted Halloween was dangerous for allowing children's imagination to run wild. As Louis asked Crowley more about his mandate, Fairweather sneaked off. Slimer caught on and followed him. Egon attempted to explain Halloween's cultural significance but Crowley refused to listen. Instead, Winston told Slimer there were candy in the visitors' socks. Crowley and Fairweather ran for it. The guys turned them down, but one of their P.K.E. Meters was stolen by Fairweather when Slimer was distracted by news about candy. Crowley recalled he needed a P.K.E. Meter to help focus his machine. Fairweather revealed the stolen equipment. Not dwelling too long on the moral implications, the duo raced back to Crowley's home.
At Jefferson Junior High, the Ghostbusters put on a rally for the students. Once Egon activated a light show, the guys sang about the history of Halloween. Slimer grabbed a girl dressed as a ballerina from the audience and danced with her while Peter tried to flirt with one of the teachers. Meanwhile, at Crowley's home, Fairweather finished the last of the modifications for the machine, the Electronic Positronic Anti-Halloween Machine (AHM). Once Crowley activated it, the AHM scanned the city and destroyed anything related to Halloween - pumpkins, decorations, costumes, candy, and books. However, something very bad happened. A portal opened in the sky above Crowley's home. A very large demon named Boogaloo and his minions crossed over into New York City. Fairweather revealed Crowley was just a pawn in a plan to open a door to the Other Side. He then revealed his true form - that of a monster!
In the city, the Ghostbusters rescued a mother and infant from a pair of winged monsters. However, the city was infested and Egon worried they were doomed. Ray, however, believed it wasn't time to give up yet. Boogaloo and his minions converged on Times Square and celebrated their victory. The Ghostbusters observed a news report from an electronic store display and learned the President declared a national state of emergency. Boogaloo took over the airwaves and declared the ghosts were in charge because the Halloween Deal was broken. Slime gushed out of the television sets and landed all over the guys. Egon explained how Earth was once infested with demons 2000 years ago but the Druids struck a deal. The worse of the demons moved to the Netherworld on one condition, they would be remembered on one day - Halloween. Egon believed if they didn't restore Halloween by midnight, the contract would be broken permanently. Peter looked at his watch. It was 11:30 pm. Winston realized the Containment Unit was a prime target.
At the Firehouse, Janine, Louis, and Slimer struggled to keep an army of ghosts from entering the basement. Several got through and opened the Containment Unit. Slimer quickly flew Janine and Louis to safety as the unit exploded. From a distance, the guys saw the P.K.E. surge from the explosion. All of a sudden, Ecto-1 fell apart and a bunch of ghosts fled the scene. Out of Ghost Traps and 10 minutes of power left on the Proton Packs, Ray was ready to give up. Peter declared all they had to do was find the door and close it. Egon checked his P.K.E. Meter and pointed towards the Times Square district. Boogaloo stood in their way. While Egon and Winston raced to reverse the AHM, Peter and Ray were left to distract Boogaloo. When Egon and Winston arrived at the mansion, the AHM was fatally sabotaged by several ghosts. Boogaloo toyed with Peter and Ray and animated part of the street to capture them. Egon, Winston, and Crowley were paid a visit by a girl who lived next door, Irma. She was dressed like a Ghostbuster and wanted to help out, stating she wasn't afraid.
Egon realized this was the solution. With two minutes until midnight, Irma was presented to Boogaloo. He was perplexed at her lack of fear. Egon stepped in and inferred Halloween was about the rediscovery of wonder and taking back the night for the children. The Halloween Deal was restored and a portal opened up and pulled Boogaloo and his forces in. Time was also restored backwards to 8 pm. Irma parted ways to meet up with her father and the gang decided to go trick or treating for Halloween.
|Frank Welker|| Raymond Stantz|
|Dave Coulier||Peter Venkman|
|Buster Jones||Winston Zeddemore|
|Rodger Bumpass|| Fairweather|
|Maurice LaMarche||Egon Spengler|
|Kath Soucie|| Janine Melnitz|