When holiday festivities are dampened by the murder of a pastor of the nearby St. Agatha's Church on St. Patrick's Day, the Sisters of Mount St. Francis College are confronted with a host of underhanded goings-on to investigate. Someone has been embezzling funds from the church; and its pastor, the late Monsignor Joseph Higgins, seems to have been a man with many enemies. Spry septuagenarian Sister Mary Helen and her sidekick, Sister Eileen, have their hands full with an abundance of suspects. Six prominent members of the congregation all seem to have the motive and the opportunity to poison the Monsignor, as does his disagreeable housekeeper. And all of them seem to feel very strongly that he got his just desserts. Merry mayhem ensues as the nosy pair of nuns delve into the much-disliked Monsignor's dirty past to uncover the killer.