Wealthy American Jervis Pendleton III has a chance encounter at a French orphanage with a cheerful 18-year-old resident, Julie Andre. He anonymously pays for her education at a New England college. She writes letters to her mysterious benefactor regularly, but he never writes back. Her nickname for him, "Daddy Long Legs", is taken from the description of him given to Andre by some of her fellow orphans who see his shadow as he leaves their building.
Several years later, he visits her at school, still concealing his identity. Despite their large age difference, they soon fall in love.