Standing Room Only (S04E04)

It's spring and a hay fever stricken Peter doesn't want to leave the firehouse, so he invents a ghost attractor that will bring the ghosts to them instead. Ghosts do start arriving, but it's not because of Peter's invention. It's because the ghosts are fleeing Mee-Krah, a ghost feeding entity that will destroy New York City if it isn't stopped. (Prime Video)