Suspicious of their operation, Environmental Protection Agency inspector Walter Peck asks to evaluate their equipment but is rebuffed by Venkman. Later, Egon warns that the containment unit is nearing capacity and supernatural activity is inexplicably increasing significantly. Venkman meets with Dana and informs her Zuul was a demigod worshiped as a servant to "Gozer the Gozerian," a shape-shifting god of destruction. When Dana returns home she is possessed by Zuul; A similar entity possesses her neighbor, Louis Tully. Venkman arrives and finds the possessed Dana/Zuul claiming to be "the Gatekeeper." Louis is brought to Egon by police officers and claims he is "Vinz Clortho, the Keymaster." The Ghostbusters agree to keep the pair separated.