A provincial chemist's daughter is to marry her cousin Gilbert.The day before he arrives,a stranger ,who has just escaped from an insane asylum ,claims he is the famous cousin.He wins them over,father and daughter.The latter spends the night under the stars with the unknown person she calls Jupiter.Much to her mother's displeasure ,deeply shocked at her daughter's behavior.But daddy is on the lovers' side .Then the true relative makes his entrance.