From an ominous Lecturer, a small 1930s middle American community learns of the Harper Affair, in which young Jimmy Harper finds his life of promise turn into a life of debauchery and murder thanks to the new drug menace marijuana. Along the way, he receives help from his girlfriend Mary and Jesus Himself, but always finds himself in the arms of the Reefer Man and the rest of the denizens of the Reefer Den.
