My Little Sister (1919)

A woman writes about her sister's tragedy, vowing to help others in similar situations: Because Bettina longs to leave her country home, her loving mother sends her and her serious-minded elder sister to London, accepting their aunt's invitation to visit and allow Bettina to be introduced to society. The girls' dressmaker steals the aunt's photograph and sends it to a woman who, disguised as their aunt, leads the girls to a brothel. After the elder sister escapes, aided by her concerned male companion, she races in a cab to her aunt's home, but is frustrated in her attempt to rescue Bettina by her aunt's infirm state, the inefficiency of the police, and her own inability to remember the location of the house. She finds her cab driver, but he is drunk and soon dies in an accident. After falling ill, the sister, convinced by a dream that Bettina has died, resolves to devote her life to saving other women.

Unfortunately the movie My Little Sister is not yet available on HBO Max.