Leon Errol, an author who is an expert on child-behavior, marries a widow who has a ten-year-old boy who is a terror of a brat. The kid is taken along on the honeymoon train. He makes himself a nuisance from the start, and keeps his new stepfather up all night entertaining him because the boy can't sleep. Their antics also keep all of the rest of the passengers in the sleeping-car awake.