Two brothers, Tim and John Branner, are driving through the Louisiana swamps when their car gets stuck in mud. John tells his young brother Tim to find a pole to leverage them out, but Tim refuses and John goes looking. As he picks up a large branch, he hears an unearthly squealing noise and goes to investigate. He finds a Southern plantation house with large numbers of pigeons on the front yard. John approaches the manor and the same noise echoes out. The pigeon fly at his face, blinding him, and John yells for Tim to come. When his brother arrives, John insists that the pigeons deliberately attacked him. Tim starts to go into the manor and John hesitates, and then follows him in.
The brothers enter the front hall and realize that no one has been in the mansion for many years. Tim goes to get the sleeping bags and tells John that they need to sleep for the night before continuing on. Once he leaves, John examines the portrait of a woman hanging above the fireplace. When Tim returns and starts a fire, John nervously eyes the pigeons sitting on the eaves of the manor. The brothers go to sleep, but John is woken up by a woman singing. He follows the singing upstairs, while Tim wakes up and starts to go after him. He hears his older brother scream and runs to investigate, and finds John holding a hatchet with his head smashed open. He advances on Tim, seemingly in a trance, swings, and just misses. Tim runs outside into the woods and finally trips, knocking himself unconscious.
Later, Tim wakes up and finds himself in a cabin. The county sheriff, Buckner, introduces himself and explains that the cabin owner, Howard, found Tim in the swamp. Tim finally tells Buckner what happened and the sheriff realizes that Tim is talking about the Blassenville Plantation. He tells Howard to get his shotgun and come with him, but Howard panics and runs off into the swamp. Buckner asks Tim to come with him and the teenager reluctantly agrees. They enter the manor and Bucker finds the blood that dripped from John. He follows the trail to the main room, where John's corpse is resting on his sleeping bag, still holding the hatchet which is thrust into Tim's pillow
After covering over John's body, Buckner suggests that John walked in his sleep. He asks Tim why his brother went upstairs, and Tim says that John seemed to be listening all the time since they found the manor. The teenager describes the pigeons, and Buckner says that he's never seen pigeons in the area his entire life, and there are no pigeons there now. He warns Tim that he has to hold him on suspicion of murder and suggests that they fought and Tim killed his brother. Buckner draws his gun and goes upstairs, and Tim insists on going with him. He points out the gash in the wall where John swung at him, and down the hall they find a large patch of blood. They investigate the nearest door and enter the room beyond, and Buckner's lamp goes out despite the fact it's filled with kerosene. They leave the room and go downstairs, and the lamp flares back up again. Buckner admits that he doesn't believe Tim killed his brother, and Tim asks if they can take John to town. The sheriff warns that no one else will believe Tim's story, and says that they have to wait and see what happens and if someone will reveal themselves.
After taking John's body out to the sheriff's car, Buckner and Tim wait in the main room. Tim notices the portrait on the wall and Buckner says it's Elizabeth Blassenville, the last of the three sisters to live in the manor. The other two moved away and Elizabeth finally left 50 years ago, supposedly to San Francisco to get married. They go upstairs to look around while Buckner explains that Elizabeth's father beat the slaves and many of them fled. He also beat the servant girl, Eula Lee. The only slave that remained was Jacob Blount, who is still alive. Tim and Buckner enter a different room again and find an organ, and there's no dust on the keyboard. Buckner finds a diary that belonged to Elizabeth, where she says that someone prowled the house after sunset, and all of the help ran away. The diary names Eula Lee, and Buckner wonders if the servant girl is still alive. They approach the room from earlier and notice that the door is now closed, despite the fact they left it open earlier. When they approach it, the lamp goes out and then back on again as they back away.
Buckner takes Tim to see the elderly Jacob Blount at his cabin in the woods. The sheriff tells Jacob where they were, and Jacob says that everyone there is dead but comes back at night as pigeons. Buckner asks why they beat Eula Lee, and Jacob explains that she was Elizabeth's half-sister. He warns them that if he tells them if Eula Lee is in the house, the "Big Serpent" will send a little serpent to kill him, and he promised not to tell when they made zuvembies. Buckner explains that zuvembie are female zombies, and Jacob warns that Eula Lee can command the dead, the birds, and the serpents, and only a lead bullet can kill her. They hear pigeons cooing outside the door and Jacob refuses to say anything else. He goes to feed more wood into the fireplace and a snake bites his hand. Before they can do anything, Jacob dies, and Buckner says they'll come back for the body in the morning. Tim wonders if Eula Lee was responsible, but Buckner insists that it was an accident.
When Buckner and Tim return to the house, they discover that pigeons have covered Buckner's car. As they wait inside the house, Buckner loads his gun and Tim wonders what they'll do if nothing happens. The sheriff says that they'll have to take John's body in and hope the authorities believe them. He tells Tim to get some sleep and sits at the door. A little later, Tim wakes up from a nightmare and discovers that Buckner is gone. The teenager starts to go upstairs, but then runs down in terror. After a few seconds, he hears a woman singing and goes up the stairs, entranced like his brother was earlier. The aged Eula Lee emerges from hiding and approaches Tim with an axe. Buckner emerges from hiding and shoots her, and she retreats into the room. The sheriff shakes Tim out of the spell and tells them to stay there while he goes after Eula Lee.
Buckner finds a hidden passage behind the fireplace and finds a room filled with mementoes... and three female skeletons, their heads smashed in. Tim follows him in and they find Eula Lee lying on a couch, dead from the lead bullet Buckner shot her with.