In this youthful comedy, a child genius has fun getting her cousin into trouble. The bright girl's parents take her and her nephew on a sea cruise to Paris. En route, the girl treats the boy abominably. First she pushes him over the boat, then she stuffs him down an airshaft. Later she sticks his head in a fishbowl. When she is not bedeviling her cousin, she is helping her father get out of trouble with con artists.