One day last April, copper-cheeked Margarito Castro planted corn on his hillside acre near Guatemala's volcano-ringed Lake Atitlán and prayed to the Virgin and a host of saints that rain might be plentiful and the harvest good. One morning last fortnight, after a plentiful harvest, Castro loaded the first quintal (100 lbs.) of corn into a dugout canoe and, with his two eldest sons, paddled across the deep-blue lake to the market in Panajachel.
A steady rain was falling when Castro awoke in Panajachel the next morning, and he decided to stay on another day. Twenty-four hours...