When master swashbuckler Gil de Berault (Conrad Veidt) is sentenced to death for sword-fighting -- which has recently been made illegal -- Cardinal Richelieu (Raymond Massey) offers to spare his life if he will capture a duke (F. Wyndham Goldie) suspected of organizing an uprising. De Berault obliges and arrives at the duke's home, where he struggles to complete his mission amid aroused suspicions and unwittingly falls for the duke's alluring sister, Marguerite (Annabella).