The Scaring of the Green

S5 E5: When the Ghostbusters are arrested for accidentally/nearly killing the mayor's wife, the deputy police chief, O'Malley, makes a deal with them to get them out of their predicament. According to him, an ancestor of his stole a pot of gold from a leprechaun, which caused the leprechaun to curse the O'Malley family line. Every St. Patricks Day, during a full moon, a Bog Hound rises up and seeks out the head of the O'Malley clan, which is the deputy police chief, to carry them off. The only thing that can stop the Hound, is a Four-Leaf Clover. The Ghostbusters search the city for a four-leap clover, while Egon goes alone to try to catch the Bog Hound with 'science'.