Act 1    Rose Maybud and Robin Oakapple indirectly confess their love for each other.  Robin's foster-brother Richard Dauntless arrives home from the sea, and speaks to Rose on Robin's behalf.  Rose misunderstands and falls in love with Richard.  Discovering this, Robin declares openly his love for Rose and they agree to marry.  On their wedding day, however, things do not go according to plan.  The evil Baronet of Ruddigore, Sir Despard Murgatroyd, arrives to claim young Robin as his elder brother, Sir Ruthven Murgatroyd, and thus the rue Baronet.  Rose, brokenhearted, rejects Robin and returns to Richard and the reformed Sir Despard agrees to marry his old flame Mad Margaret.

Act 2    Sir Ruthven and his servant Adam bewail the witch's curse imposed on his family - to commit one crime every day or else perish in agony.  Richard and Rose arrive to ask his permission to marry.  Forced to yield, Sir Ruthven declares he will not commit another crime and begs his ancestors for mercy.

The portraits, led by his late Uncle Sir Roderick, come to life and force him to abduct a village maiden.  Rose's aunt, Dame Hannah, is mistakenly taken and she threatens Sir Ruthven with a dagger.  Sir Roderic saves him and is reunited with his former fiancé.  Sir Ruthven declares that he has found a way to foil the curse and he and Rose are finally reunited.