Sir Basil Algernon Winterton is an elderly nobleman in poor health who decides to seek out his illegitimate children around the world so that he can know them before he dies. Antoinette "Toni" Flagg is a girl from America whose mother died when she was young, and she is summoned to England by Sir Basil's henchman.
Once there, she meets her brother and sister, also brought here for the first time, and together they meet their father and begin to know him. While initially he bristles at their individuality, with Toni especially grating his patience, he soon comes to love them all. One day however, Toni discovers that it was actually her half sister, 20 years deceased, who was Sir Basil's daughter, and she is of no relation to him. While she tries to tell Sir Basil, his love for her (and hers in return) prevent her from doing so, but when it eventually comes out, he suspects her of betraying him and sends her away.
Heartbroken, Toni tries to leave London by joining a risky trans-Atlantic flight back to New York. Hearing this, Sir Basil realizes how much he cares for Toni and tries to stop her before it's too late.
