Judy Abbott is an orphan living in New York, who at the age of 17 finds herself in receipt of a college scholarship and monthly allowance from a mysterious benefactor. Her benefactor believes she has great potential as a writer and wishes to see her succeed. The only payment he asks in return is that she write him a letter every month addressed to the pseudonym "Mr. John Smith", with the understanding that he will never reply.

Wealthy American, Jervis Pendleton has a chance encounter at a French orphanage with a cheerful 18-year-old resident, and anonymously pays for her education at a New England college. She writes letters to her mysterious benefactor regularly, but he never writes back. Several years later, he visits her at school, while still concealing his identity, and—despite their large age difference—they soon fall in love.