Jerusha Abbott is the "Oldest Orphan in the John Grier Home" until a mysterious benefactor decides to send her to college to be educated as a writer. Required to write him a letter once a month, she is never to know the benefactor's identity so she invents one for him: Daddy Long Legs. Although she knows that he will never respond to her letters, she grows more and more fond of this elusive and kindly "old" gentleman.
But another relationship soon begins to develop in Jerusha's life. Jervis Pendleton is the well-to-do "youngish" uncle of one of Jerusha's roommates, who introduces her to a world of literature, travel, and adventure. Through her correspondence with Daddy Long Legs and her growing intimacy with Jervis, Jerusha's letters chronicle her emergence as a delightfully independent "New American Woman." Yet there is one startling fact Jerusha has yet to recover, one that will change her life forever.