The Firefly of France (1918)

The "Firefly of France" is an elusive master criminal of uncertain loyalties. When the Firefly disappears from view with a satchel of important government documents in his possession, his sister Esme Falconer is suspected of beings in cahoots with him. Dashing aviator Devereaux Bayne believes in Esme's innocence and accordingly dons civilian garb and heads to Paris' Latin Quarter to get the low-down on the Firefly's whereabouts.