A magical English nanny takes over the household of a proper London banker, changing the lives of everyone, especially his two naughty children.

It follows the exploits of eleven-year-old Alexander as he experiences the most terrible and horrible day of his young life, a day that begins with gum stuck in his hair, followed by one calamity after another. But when Alexander tells his upbeat family about the misadventures of his disastrous day, he finds little sympathy and begins to wonder if bad things only happen to him.

After Mary Poppins departed London, Jane and Michael Banks grew up into loving and responsible adults. When Michael becomes a single father of three children after the death of his wife, Mary Poppins revisits the Cherry Tree Lane home again to try to help Michael and his family cope and move beyond their grief. Time passes quickly for most normal mortals. Mary Poppins has never been normal. Although it's now the 1930s, she looks exactly the same....