Anna Pigeon, a ranger for the U.S. Park Services, sets off on vacation - an autumn canoe trip in the to the Iron Range in upstate Minnesota. With Anna is her friend Heath, a paraplegic; Heath's 15-year-old daughter, Elizabeth; Leah, a wealthy designer of outdoor equipment; and her 15-year-old daughter, Katie. On their second night out, Anna goes off on her own for a solo evening float on the Fox River. When she comes back, she finds that four thugs, armed with rifles, pistols, and knives, have taken the two women and their teenaged daughters captive.