Darling Lili (1970)

She gave away secrets to one side and her heart to the other.

World War I. Lili Smith is a beloved British music hall singer, often providing inspiration for the British and French troops and general populace singing rallying patriotic songs. She is also half German and is an undercover German spy, using her feminine wiles to gather information from the high ranking and generally older military officers and diplomats she seduces.