In which episode do Mulder and Scully investigate a deadly suburban black sludge that comes out after sundown?

This is the episode where Mulder and Scully go to suburbia, posing as a married couple, to investigate a deadly black sludge that comes out after sundown. When they arrive at their new utama the neighbors frantically get them moved in before sundown. Mulder hypothesizes that the utama owner's association president is behind the black sludge and confronts the man telling him that he created this thing and every tahun he has to renew his vows in the Tibet.