 A wave of spontaneous combustion is sweeping through South Park, and the mayor charges Stan s father (a geologist) with finding the cause. After working feverishly on the problem, he finds the answer: people are holding in their farts for so long, they re bursting into flame. A grateful nation loosens its sphincters in relief, but their problems aren t over yet. Meanwhile, the boys crucify Cartman in the hopes of helping Kyle s father get an erection.