The operetta opens in the village of Rederring, with a troupe of professional bridesmaids who are out of work. They are distressed because the beautiful Rose Maybud will marry none of her suitors, since she is secretly in love with Robin Oakapple, a local farmer. The bridesmaids therefore try to persuade Rose’s aunt, Dame Hannah, to marry Robin’s faithful servant, Old Adam, so that they do not lose their endowments. Hannah refuses, saying that she is pledged to maidenhood. She had a lover in her youth, but he turned out to be the cursed bad baronet, Sir Roderic Murgatroyd of Ruddigore, who was condemned to commit an evil deed every day forever.
Dame Hannah reproaches Rose for not returning the love of any of her suitors, but Rose complains that all the men of the village are too bashful, and it would be unbecoming of her to encourage them. Rose herself is a foundling, and bases her life upon a book of etiquette that was left with her when she was a baby. Robin Oakapple enters, and it is clear that there is a spark between himself and Rose, but both are too shy to admit it properly.
Robin is really Sir Ruthven Murgatroyd of Ruddigore, but he fled from home at the prospect of inheriting the curse, and has lived in the village of Rederring ever since. At this point Robin’s foster brother Richard Dauntless returns home from sea, and is promptly consulted by Robin about his love for Rose. Richard, who does everything according to the dictates of his heart, offers to speak to Rose on Robin’s behalf. Of course, he promptly falls in love with her, and woos her for himself. Robin is stunned by the news of the couple’s rapid engagement, and while apparently being happy for them, makes several insinuations about the unsavoury natures of sailors which cause Rose to choose him over Richard.
At this point Mad Margaret appears. She is looking for Rose, having heard that Sir Despard Murgatroyd, the current bad baronet of Ruddigore, plans to carry off Rose as one of his daily crimes. Mad Margaret is in love with Sir Despard, and so wishes to prevent such a course of events. Rose reassures Margaret that she is pledged to another.
Unfortunately for the happy couple Richard is aware of Robin’s true identity, and to get revenge on his foster brother he tells Sir Despard that Robin is really his older brother Sir Ruthven Murgatroyd, the true bad baronet. Sir Despard is desperate to get rid of the curse, and so breaks up Robin’s wedding by revealing the truth. Rose is distressed, but ignoring Richard, promptly offers herself in marriage to Despard. However Despard, now a virtuous young man, refuses, saying that he must keep an earlier promise to marry Margaret. Robin collapses insensible at Rose’s feet.
The second act takes place in the picture gallery at Ruddigore Castle, where the walls are lined with portraits of the dead baronets. Sir Ruthven and his servant Adam are worn out by the effort of having to commit a crime everyday, and are having problems thinking up their dastardly deeds. Adam’s newest idea is to poison the beer of Richard and Rose who have come up to the castle to ask for permission to marry. Sir Ruthven is not yet as bad as that, and rejects the idea. He does however threaten to imprison Rose in a dungeon. Richard promptly brandishes a small Union Jack flag, a signal that not even the Bad Baronet of Ruddigore can defy, and Rose is saved. Sir Ruthven therefore permits the two of them to marry.
As night approaches, the figures in the picture frames of the gallery begin to come to life, and the late Sir Roderic Murgatroyd steps out of his frame and reproaches Ruthven for not fulfilling the curse. Sir Ruthven begins to make excuses: on Monday it was a Bank Holiday, but on Tuesday he made a false income tax return, on Wednesday he forged his own will, and on Thursday he killed a fox … This is just not good enough for Sir Roderic and, to encourage his nephew to do better, he gives Ruthven a taste of the torture to be expected if he fails in his task.
Sir Ruthven promptly orders Adam to go to the village and carry off a maiden as today’s crime. A reformed Despard and Margaret come to plead with Sir Ruthven to mend his wicked ways. Despard points out that although Ruthven has only been bad for a week, he is, in the eyes of the law, guilty of the crimes Despard committed in his stead for ten years.
Adam now returns, having carried off Dame Hannah for his master. Hannah promptly tries to attack Sir Ruthven with a knife. Terrified, he calls on his late uncle, Sir Roderic, to come to his aid. He recognises Hannah as his former sweetheart, and orders everyone else to leave them alone. The two have a brief moment together, before Sir Ruthven rushes back in, having had a brainwave. He believes that whilst a Baronet of Ruddigore who refuses to commit a crime must die, that refusal is itself tantamount to suicide. Since suicide is deemed a crime, the only thing he must do each day therefore is refuse to commit a crime, and his curse will be fulfilled. This is all very satisfactory, particularly since Sir Roderic should therefore not have died, and may be counted as being alive again. Roderic is then reunited with Hannah, as much as a ghost may be, and Rose returns to Sir Ruthven. Richard accepts his lot philosophically, and marries Zorah, the chief bridesmaid.
Synopsis by Rae Lamond
[You can find an extended plot summary and other material in the Gilbert and Sullivan Archive]