The Vampire Bat (1933)

When the villagers of Klineschloss start dying of blood loss, the town fathers suspect a resurgence of vampirism. While police inspector Karl remains skeptical, scientist Dr. von Niemann cares for the vampire's victims one by one, and suspicion falls on simple-minded Herman Gleib because of his fondness for bats. A blood-thirsty mob hounds Gleib to his death, but the vampire attacks don't stop.