A young husband and wife on summer vacation rent a house in a small town called Willow, Maine, only to be warned repeatedly (if vaguely) to leave by the local inhabitants. They do not comply and, having purchased groceries, return to the house. They never learn the price for prosperity the citizens of Willow must pay: every seven years a husband and wife will come there from outside and will stay, despite protests, to become sacrifices during the rainy season. When the "rain" starts, the couple does learn the nature of the precipitation: an army of grotesque black toads the size of footballs, armed with needle-sharp teeth, and able to chew through doors and walls...