This film in the Southern Gothic season also screens on 10th May. Full details here.
Chicago Reader review:
Don Siegel and Clint Eastwood took time out from their popular series of Universal programmers for this very personal exercise in American gothic (1971)—one that should have played the art houses rather than the drive-ins. Eastwood is a wounded Union soldier stranded in Confederate territory, who finds refuge of a sort in a girls' school run by Geraldine Page. The film is hushed and evocative, full of menace and barely suppressed hysteria. With Elizabeth Hartman.
Here (and above) is the trailer.