Samhain, trapped inside the Containment Unit at the Firehouse, begins chanting to grow in power. Ghost sightings across the city rise at an alarming rate. Meanwhile, the Ghostbusters are airborne in their custom zeppelin when flying goblins attack the craft. Egon Spengler triggers the floodlights, scattering the goblins, but the incident reveals a grim implication: if goblins are attacking and Halloween is approaching, Samhain must be close to breaking free.
Back at the Firehouse, Louis Tully suits up in Ghostbusters gear and goes to the basement to investigate the chanting. Samhain emerges. Janine Melnitz manages to radio Egon on the blimp and begins describing the situation before the transmission cuts out.
The zeppelin arrives at New York harbor to find the city draped in an unnatural darkness, spirits visible everywhere. A second wave of goblins attacks. This time the team deploys a pterodactyl camouflage unit mounted atop the blimp, which drives off the attackers. Because New York is too dangerous to land in, the Ghostbusters divert to Lakehurst, New Jersey. Samhain is left free to reveal his larger plan.
The team links up with Phineas Evantide, a druid with a plan to counter Samhain. Evantide travels to Europe to join the European druids and add his magic to their chants, working to weaken Samhain from a distance. Simultaneously, the Ghostbusters head directly to Times Square to confront Samhain. While the confrontation unfolds, Tarantula, Evantide's familiar who has been traveling with the team, slips away and rescues Janine, Louis, and Slimer from Samhain's grip. The combined druidic magic eventually overwhelms Samhain and forces him back into the Containment Unit. To prevent a repeat escape, the Ghostbusters install a horn in the Containment Unit: whenever Samhain starts chanting, the horn interrupts his concentration.
