ACT I
In the reign of James I, Sir Rupert Murgatroyd, first Baronet of Ruddigore, ruthlessly employed his time and money in the persecution of witches. The legend runs that one of his victims in her last agonies set a terrible curse upon the family prophesying that each succeeding holder of the title would be compelled to com-mit a crime daily, or in default perish in torment. Each of the hapless Baronets after conforming with the terms of the curse for a time has subsequently revolted, and then died.
The play opens in the little fishing village of Rederring, which is quite close to the estates of the Murgatroyds, and it is remarkable for the fact that it possesses a corps of professional bridesmaids (supported by charity).
Robin Oakapple, a young farmer, is secretly in love with Rose Maybud, the most charming maiden in the village, but is too diffident and shy to press his suit, so that he enlists the aid of Richard Dauntless - his foster-brother and a man-o'-wars-man - to woo her. This was really an unfortunate arrangement as Richard, in the course of his wooing for Robin, becomes engaged to Rose upon his own account. However, upon it being mentioned to the maiden that Richard was only Robin's deputy she quite readily transfers her affections to Robin.
Now Robin Oakapple is really Sir Ruthven Murgatroyd, the rightful Baronet, but he has lived for years the simple life of a farmer in order to escape from the family curse, and has apparently established the belief that Sir Ruthven is dead. Meanwhile, the estates with their troublesome and undesirable encumbrance are in the hands of his younger brother, Sir Despard Murgatroyd.
Upon Robin becoming engaged to Rose Maybud, Richard's heart, which is always rather troublesome, urges him to impart the true state of affairs to Sir Despard, who is overjoyed to be relieved of the curse and claims Robin as his elder brother and the rightful heir. This also brings to an untimely end the courtship of Rose and Robin.

ACT II
The scene opens in the Picture Gallery at Ruddigore Castle, with Robin, now Sir Ruthven Murgatroyd, contemplating the portraits of his ancestors. For a week past he has been forced to perform one crime a day, but has managed to limit his activities to only trifles, such as making a false income tax return, and forging his own will. This shuffling does not please his ancestors, and they leave their picture frames to call him to account. It is finally decided that to escape the most unpleasant death he must carry off a lady, and Adam (Robin's old and faithful servant - now his valet de chambre) is despatched to carry off a maiden.
Now enter the reformed Sir Despard and Margaret (Margaret was formerly the mad girl of the village). They are an extremely pious couple, District Visitors in fact, and they endeavour to make Sir Ruthven (Robin) mend his evil ways. No sooner have they departed than Adam ushers in "the maiden" who proves to be none other than Dame Hannah (Rose Maybud's aunt), an old lady who years ago was engaged to be married to Sir Roderic (one of the former Bad Barons). That engagement too was quickly cancelled upon Hannah finding out the true identity of her lover. She attacks Robin with vehemence and upon her drawing a dagger he calls upon the ghost of Sir Roderic to save him. The deceased Bad Baron thereupon springs to the stage, and Hannah and he instantly recognise one another as long-lost sweethearts. They are reconciled, and Robin suddenly conceives the brilliant idea that, as with the Ruddigore Baronets the refusal to commit a daily crime - with the knowledge that certain death is the penalty of such refusal - is practically suicide, and suicide being in itself a crime, it follows that Sir Roderic should never have died, and is consequently still alive. This is agreed to and Sir Roderic assumes the title, apparently freed from the curse, while Robin again successfully woos Rose Maybud, and Richard has to be satisfied with Zorah, the principal bridesmaid, upon which solution the curtain falls.