Blackwater. I The flood by Michael McDowell

As the dark and menacing waters of the local river submerge Perdido, a small town in the south of Alabama, the Caskeys - a family of rich landowners - must confront the tide of damage caused by the flood. Led by Mary-Love, the powerful matriarch, and by Oscar, her devoted son, the family must pick itself back up. But what they haven't anticipated is the sudden appearance of Elinor Dammert - a mysterious but seductive young woman with a troubling past. Her sole ambition appears to be to infiltrate the very heart of the Caskey clan.