Nothing But the Truth (1941)

Gwen Saunders teams up with her uncle's employee, Steve Bennett, in an attempt to double her $10,000 investment in the family firm. If she can reach the $20,000 mark, her uncle, T.T. Ralston, will match the figure. Steve bets that if he can spend an entire day without telling a lie, Ralston and his business partners must double Gwen's money. Bennett then earns the enmity of everyone involved in his attempt to win the bet.