The White Sister (1923)

Lillian Gish is the daughter of a rich Italian count who is killed in a fall from his horse. Though Lillian stands to inherit a large estate, her older half-sister burns the will and thus inherits the property herself, throwing Lillian into poverty. Fortunately, she is engaged to marry the dashing officer Ronald Coleman, but he is captured by Arabs on an expedition to Africa. Dedicating her life to his memory, Lillian becomes a nun, unaware that her lover has escaped his captors and returning to Italy! The climax takes place against a backdrop of the eruption of Mount Vesuvius.