An account of the life of Catherine the Great. Young Catherine (Elisabeth Bergner), an Austrian princess, is engaged to marry Peter (Douglas Fairbanks Jr), the Grand Duke of Russia. The marriage is arranged by Empress Elizabeth (Flora Robson), Catherine falls in love with Peter and moves to Russia to be with him. However, when Elizabeth dies Peter's mental health deteriorates, and he becomes a tyrannical ruler. It is up to Catherine to calm the people of her new country and attempt to take over affairs of state.