Little Boy Blue.

Living in rural Texas is a dysfunctional family: an abusive dad, a Vietnam vet with a war wound that's left him impotent; a compliant wife and a son of about 20, two small sons who look a lot like their brother. The dad harbors a secret, and he goes to murderous lengths to keep it hidden. The young man, Jimmy, who has suspicions, but little comes out until a Yankee woman comes to town.