Like every year, Jim, Ray, Brad and Paul leave the town for a week to go hunting in the woods. But this year everything is different: There's not a single animal to be found, the whole forest has fallen quiet. Two female campers they meet have mysteriously disappeared the next day, leaving their whole equipment behind. And then they start to behave weird themselves... An alien ...

解放前，江西血吸蟲病肆虐，方老爹（錢千里 飾）、方媽媽（上官云珠 飾）一家逃難來到浙江，怎知這里也是該病重災區(qū)。不久，方老爹病死異鄉(xiāng)，兒子冬哥（徐志驊 飾）被抓丁，童養(yǎng)媳苦妹子（尤嘉 飾）無奈之下另嫁他人。解放后，黨和政府為了根治血吸蟲，成立了血防站，并從上海派來醫(yī)生指導群眾群防群治。此時苦妹子的丈夫已患病死去，她自己也患了病，在血防站意外重逢失散多年的冬哥，兩人述說離別之苦，冬哥對她的遭遇充滿同情。方媽媽也終于見到失散十年的苦妹子，當知苦妹子患了血吸蟲病，她十分揪心，因擔心兒子也被感染，她勸兒子離開此地，但善良的冬哥不愿放棄他深愛著的苦妹子。毛主席視察病區(qū)后，全國組織有關行業(yè)下大氣力,采取標本兼治，苦妹子有救了......