According to the site:
The story begins 4000 years ago with a strange cult mourning the death of Dumazu, an ancient demon of death and destruction. Fast forward to 1989, when museum curator Janosz Poha is sent to a mental institution following the events in Ghostbusters 2. There he meets Ismael, the self-proclaimed last member of the cult of Dumazu. Ismael seeks a Shard of the Relic of Nilhe, a mystic artifact that possesses the power to bring Dumazu the Destroyer back to life, and he tasks Janosz with obtaining it. Janosz’s reward: Dana Barrett.
Some years later, following Janosz’s release from the mental institution, a wave of unusual paranormal manifestations start appearing all over New York City. The Ghostbusters can’t handle all the heat with this latest outbreak, so they recruit a young group of paranormal studies enthusiasts to lend a hand. And that’s where you come in, guiding the rookie team in their first adventure to find the truth behind Ismael, the Relic of Nilhe, and Dumazu the Destroyer!
After Vigo, it seems Janosz needed a new supernatural buddy.
