Orphaned, 18-year-old Billy Neilson writes to her father's boyhood friend, William Henshaw, for whom she was named, asking whether she can make her home with him. Thinking her a boy, he and his two brothers agree to take her in to their bachelor quarters. To their consternation and delight, she turns their lives topsy turvy -- until a well-meaning busybody makes it clear just how much she's upset their previously placid existence. Ultimately, the story turns into a tame farce of mixed-up love affairs, but Miss Billy and her cohorts are charming.