Ruddigore, written by Gilbert and Sullivan is the story of the small fishing village of Rederring. The village has a group of professional bridesmaids, who have nothing to do due to the lack of weddings. Because of this the bridesmaids try to persuade Dame Hannah to marry Adam. Hannah, however cannot marry because she is pledged to eternal maidenhood. A long time ago, she married a young man who was under an assumed name. On the day they were to be married, she discovers that he was Sir Roderic Murgatroyd, one of a cursed family.

Hannah explains to her niece Rose, the village beauty, that Sir Roderic's ancestor sir Rupert Murgatroyd had persecuted witches, and one of his victims had gotten the best of his by putting this curse on him: ""Each lord of Ruddigore, despite his best endeavor, shall do one crime, or more, once every day, for ever." The penalty for defying the curse was death by torture on the day the crimes cease. Each lord of Ruddigore had died this way.

Hannah is upset that Rose will not marry a youth, but Rose responds that all the youth are too bashful and it would not be fitting for her to make the advance.

In the mean time there is Robin Oakapple, whom Rose is in love with. Robin is however really Sir Ruthven Murgatroyd, but because he did not want to inherit the curse, Ruthven fled his home and has been living under the assumed name of Robin. Ruthven's younger brother, Despard, believing Ruthven is dead has inherited the curse upon himself.

Robin's foster brother Richard, returns home from sea, and Robin tells Richard how he is in love with Rose, but his shyness is preventing him from doing anything about it. Richard decided that he will help Robin out and speak to Rose for him. This does not go well though, because Richard sees Rose and falls in love and forgets Robin. Robin however, is quite clever and makes some remarks about the less than respectable aspects of a sailor's life, which causes Rose to leave Richard and return to Robin.

Despard plans on taking Rose as his crime for the day, but Richard enters, and to get back at Robin, he reveals to Despard that Ruthven is living as Robin. Despard is overjoyed. They act quickly, because Robin and Rose are set to be married, and upon finding them, Despard challenges Robin. Ruthven cannot hide who he is, so Rose leaves him and returns to Richard.

Sir Ruthven goes to live in the Ruddigore Castle with his servant Adam. One of the hallways is a picture gallery where full length portraits of the Baronets of Ruddigore from throughout history hand. Sir Ruthven and Adam are trying to think of a crime to commit for that day, Adam suggests poisoning the beer of Rose and Richard who will be coming to the castle that day. When Rose and Richard arrive Sir Ruthven cannot go through with it, so they leave unharmed.

Then the picture gallery comes alive. The portraits have become animated and they are angry with Sir Ruthven for having failed to fulfill the curse for that day. Sir Ruthven realizing who they are makes up excuses as to why he hasn't committed a curse. These excuses do not satisfy the ghosts, so they give him a taste of the torture that will come if he fails to commit some real crimes.

Sir Ruthven tells Adam to go to the village and carry off a maiden. Then Sir Despard and Margaret arrive and tell Ruthven that in the eye of the law, he is responsible for all the crimes committed by Despard during the past ten years. Ruthven is appalled and determines to reform and take the consequences.

Meanwhile, Adam returns with Dame Hannah, who seizes a sword and comes after Ruthven. Sir Roderic, to help his nephew steps from the picture, and immediately recognizes his old lover, Hannah. Ruthven leaves Roderic and Hannah alone.

A moment later Ruthven rushes in with an idea. He believes that since a baronet of Ruddigore can only die through refusing to commit a daily crime, the refusal is equivalent to suicide. But since suicide itself is a crime, Sir Roderic should never have died. This is satisfactory to everyone, so Rose returns to her first love Sir Ruthven and Richard has to take Zorah, the chief bridesmaid, and the opera ends with a joyful chorus.